Substitute My Coke for Gin.
I have overheard, and been a part of, several conversations about cooking and brewing substitutions over the past few months. Mostly relating to cooking, but a few for brewing. The conversations were split between food related allergies and the difficulties of acquiring certain ingredients. In Ealdormere I was speaking to someone about mead making and the lord wanted to know what in the hell long pepper was. I explained that it was an Indian (Indian subcontinent) relative of pepper, that is sweeter than black peppercorn. I had suggested that if he can't find any on the Internets, he can use Tellicherry peppercorns.
The purpose of this article is to discuss the art of substitutions in SCA A&S projects and feasts. When I mean substitutions, I am not referring to creating a new thing (the recipe calls for X, they knew about Y, therefore....) but in replacing one thing for a similar thing because of availability or food allergies. Black pepper can be substituted for white pepper. although it is hotter and darker. It might not be visually appealing for white sauces. Modern, farm-raised strawberries for wild ones, even though modern strawberries are larger and have a more robust flavor. Orange carrots for purple ones, because you can't get your hands on the heirloom varieties.
Replacing one item with something completely different isn't, in my opinion, a substitution. I've had General Tso's alligator, beef, and shrimp. The dish was created for dark meat chicken and while the alligator, beef, and shrimp were tasty, they weren't General Tso's chicken: different flavors and textures. replacing lamb with pike isn't a substitution, it's a new recipe, one which probably would never have been done in period since lamb was considered hot and dry and pike was cold and moist. They require different cook times and, in the minds of medieval cooks, require different herbs and spices.
I am also going to avoid gluten-free substitutions: that is something of which I know very little about. Our goal is to provide period inspired foods and beverages, and while we have access to modern food, we should avoid things that were not available to the time and place where the recipe originated. Unless we have no other alternatives. Shortening is a modern invention, but if you have to create a vegan/kosher/halal dough, you need something to replace lard.
First, I would like to say that recipes that specifically list a variety of options are not substitutions. Here, from Menagier de Paris:
#39. Seyme' of Veal
Grave' or seyme' is a winter potage. Peel onions and cook them all cut up, then fry them in a pot; now you should have your chicken split down the back and browned on the grill over a charcoal fire; and the same if it is veal; then you must cut the meat into pieces if it is veal, or in quarters if it is a chicken, and put it into the pot with the onions, then take white bread browned on the grill and soaked in broth made from other meat; then crush ginger, cloves, grains of paradise, and long pepper, moisten them with verjuice and wine without straining this, and set aside; then crush the bread and put it through a sieve, and add it to the brouet, strain everything, and boil; then serve.
This is not a substitution, this is a recipe that can be made with either veal or chicken. However, if you want to make this and do not want to use veal for conscientious reasons, you could substitute rabbit or venison. Setting aside the humoral theory, which is a different conversation, rabbit and venison, like veal, are lean and delicate in flavor (well, if you are a good hunter, venison is delicate in flavor). A good substitution for the chicken would be a Cornish hen. I would not use duck, pork, or cuts of regular beef, as these would have a different texture, and a stronger flavor, than veal and chicken. For a vegetarian alternative, use eggplant and vegetable broth.  If you are planning a feast and you know that you have to have a vegetarian dish, this will give you, the feast-o-crat, an option of making, more or less, the same looking dish for everyone. You could use turkey cutlets, but then we have to talk about did the French know about turkeys when Menagier de Paris was written. Did the French like turkey, in period. Do they like it now? I don't know, so if I were cooking a feast, I would not use turkey unless I got a really, really good deal on it.
The English did know about turkey (the birds) and they were found in London markets by the mid 16th century. I would use a whole turkey as a substitute for peacock or swan. However, peacock is drier and leaner than Butterball and swan has a lot more fat under it's skin. I've had peacock and swan, once each: the peacock tasted more like mild pheasant and swan tasted like mild duck. But if you want a large bird to dress up for high table, go with turkey. Stick a lot of peacock feathers in it's butt and no one will notice.
With access to the Internet, getting spices should not be an issue. Unless you discover at the last minute that you really, really need something that you cannot get locally. There are online resources on how to substitute one spice for another.
Apples will be easy to substitute: there are so many varieties the chances of you having access to the varieties that were available to your original cook are slim to none. Try to pick a local variety that will meet your needs; either a soft, baking apple, or a firm, crunchy apple. Sweet or tart, whichever will work for your recipe.
Oranges were bitter until the 13th or 14th century. If you need bitter, or sour, orange juice, you can substitute lemon or citron juice. If you are looking for the orange flavor, you can always add orange peel, bitter or sweet (bitter orange peel contains more pith). Keylimes cannot be substituted for limes: they taste completely different.
Orange sweet potatoes can be substituted for yellow sweet potatoes. Yellow sweet potatoes come from Africa and were known around the Mediterranean. Orange sweet potatoes come from South America and they arrived in Europe around 1520.
Check online for SCAdians describing the differences between period and modern wheat. Most modern wheat contain a lot more protein than their medieval counterparts. This can affect bread and pastries.
Many period cordials call for tansy (also known as cow bitter): please, do not use any variety of tansy. All varieties are toxic. Tansy was, and still is, used as an insecticide, a de-wormer (it's still used as that for cattle), and for inducing miscarriages. A substitute is difficult to recommend as the taste is described as either bitter or very bitter. Even recipes from the 19th century cannot distinguish the exact flavor. Alan Davidson, in "The Oxford Companion to Food", speculates that the amount of tansy used was relatively small, given its strong taste. In the BBC documentary "The Supersizers go ... Restoration", Allegra McEvedy described the flavor as "...fruity, sharpness to it and then there's a sort of explosion of cool heat a bit like peppermint." I would substitute maror, wormwood, sorrell, or even hops rather than risk anyone's health. 
On cordials; they were medicine, not for getting one's drink on. They included herbs that might have toxic properties. If you don't know what side effects an herb might have DO NOT USE IT.
Cubeb is mentioned in cordial recipes and in Arabic dishes. It is related to black pepper but has a sharper flavor. To simulate it, mix freshly ground black pepper and allspice in equal amounts. Or, order it from the Internets.
If you absolutely cannot get your hands on tahini, you can substitute peanut butter, but you might have to deal with someone's peanut allergy. Substituting pistachio nuts for pine nuts in pesto also works. Pistachio nuts are cheaper, easier to find, and are already green. This is what I use when I make pesto; I can barely taste the difference between the nuts  under all of the garlic and basil.
Low acid, white-wine vinegar with a little bit of sugar mixed in to it can be substituted for verjuice. It's not the same flavor, but it is close. Sherry vinegar can also be used.
If you have every used worcestershire sauce, you have used the equivalent of garum. Lea & Perrin did not invent the famous sauce, they were just one of the first companies to market a name brand product. If you don't want to make your own garum, and to be honest, who does.... more than once... worcestershire sauce is a suitable replacement. Thai fish sauce can also be used, but there is a big difference: Asian style fish sauces are made with soy. And, are generally more potent.
Salted herring can be replaced by tinned sardines. Please, do not substitute pickled herring. Completely different flavor and texture.
If you cannot find heirloom carrots, you can substitute parsnips. Parsnips and carrots were described as interchangeable in most medieval and Roman cookbooks. Orange carrots have a good deal of sugar in them, that's why carrot cake contains orange carrots. heirloom carrots (purple, red, yellow and white) do not contain sugar and have a starchier flavor.
Speaking of carrots, carrot leaves can used in place of parsley. They taste very similar.
Iceberg lettuce is a modern invention, and should be avoided for A&S projects. However, it is easy to find, year round, and I don't care if it is in a salad served at a feast.
Mountain cranberries, or cowberries, can be substituted with lingonberries. Lingonberries can be found at Ikea.  American cranberries can be used, but they have a tarter flavor.
Many dishes call for rooster or capon (a castrated rooster) which are not easy to get outside of a farm. Several cooks (Julia Childs, Alton Brown, Clarissa Dickson Wright) have written, and discussed on their cooking shows, that roosters lived until they could no longer perform their roosterly duties, so they were well into old age when they were killed, and have a richer flavor. Most chickens sold in the markets are pretty young, or were when they were dispatched. Capons were fattened up for eating and have a gamier taste than normal chickens. A free-range, stewing hen would be a good alternative for a rooster or capon, but they are about half the size, so you might have to change up your recipe.  I have had capon once; it doesn't taste like chicken. It tastes like what chicken should taste like.
If you can't find salt port, fatty bacon will work.
There are many recipes for porpoise. I don't know about your fish market, but mine doesn't carry porpoise. Partly because it is a mammal and not a fish. But mostly because no one wants to eat Flipper.  One book, I think that it was the "Good Housewife", has a recipe for porpoise and peas. At the end of the recipe it says that if you do not have porpoise you can use bacon in its place. But, what type of bacon? Modern bacon is leaner and "healthier" than that of twenty years ago. Most bacon isn't fully cured (it has to be refrigerated) and you will be hard pressed to find nitrate processed bacon, these days. I would go to a meat market and ask for slab bacon; as fatty as they have. Keep in mind that bacon is meat  and porpoise is fish, you cannot substitute one for the other during lent.
Lamb can be substituted for mutton, but remember, mutton has a much stronger flavor than lamb, which, in this country, is a young sheep. Mutton is at least two years old. There's not much call for mutton in the USA, even though it is delicious. When substituting lamb, make sure that you test your spice rub, gravy, or sauce so that you do not overpower the lamb. Goat can be substituted for mutton, as well, and goat is as strong of a flavor as mutton. 
There are recipes in 16th century, French cookbooks for mock venison made with mutton, red wine, and bouillon. Perhaps these recipes were for people who would never encountered actual venison because I have never had venison that tasted anything like mutton, and there is not enough red wine in the world to make me confused between the two. Clarissa Dickson Wright, in her documentary, "Breakfast, Lunch, and Dinner" did talk about how in the middle ages, venison was reserved for nobility (and poachers) and that lean pork was used to simulate venison.
Many period sources tell us that during Lent, almond milk could be substituted for animal milk; oil could be substituted for butter (almond milk can also be churned into a butter like thing); vegi broth for meat broth. Eggs? Almonds to the rescue. The Harleian manuscript lists a recipe that calls for an empty eggshell filled with an almond jelly.
Eyroun in lentyn [Eggs in Lent].
Take Eyroun, & blow owt þat ys with-ynne atte oþer ende; þan waysshe þe schulle clene in warme Water; þan take gode mylke of Almaundys, & sette it on þe fyre; þan take a fayre canvas, & pore þe mylke þer-on, & lat renne owt þe water; þen take it owt on þe cloþe, & gader it to-gedere with a platere; þen putte sugre y-now þer-to; þan take þe halvyndele, & colour it with Safroun, a lytil, & do þer-to pouder Canelle; þan take & do of þe whyte in the neþer ende of þe schulle, & in þe myddel þe ?olk, & fylle it vppe with þe whyte; but no?t to fulle, for goyng ouer; þan sette it in þe fyre & roste it, & serue forth.
Austin, Thomas. Two Fifteenth-Century Cookery-Books. Harleian MS. 279 & Harl. MS. 4016, with extracts from Ashmole MS. 1429, Laud MS. 553, & Douce MS 55. London: for The Early English Text Society by N. Trübner & Co., 1888.
Gode Cookery translation: Take eggs, and blow out that is within at the other end; then wash the shell clean in warm water; then take good milk of almonds, and set it on the fire; then take a fair canvas, & pour the milk thereon, & let run out the water; then take it out on the cloth, & gather it together with a platter; then put sugar enough thereto; then take half of it, & color it with saffron, a little, & do thereto powder cinnamon; then take & do the white in the nether end of the shell, & in the middle the yolk, & fill it up with the white; but not too full, for going over; then set it in the fire & roast it, & serve forth.
Lent substitutions are an entire article on their own. I might have to spend some time rambling about them, in the future. What I covered, here, was just what I could think of while I typed up this stream of consciousness. If you, my dear reader, has any SCA food related substitutions, please feel free to post them in the comments.
 Eggplant was known in France from the 16th century.
 Note: wormwood is also toxic, but only in very high doses. The opinion that absinthe caused madness and blindness because of the wormwood, used to flavor the cordial, is wrong. One would die of alcohol poisoning before suffering from wormwood poisoning. Absinthe gained the reputation of madness and blindness because of "bathtub" absinthe, which was often made from wood alcohol.
 Some assembly required.
 You can order capons online, but they are not cheap: pheasant is cheaper.
 Yes, Flipper was a dolphin, but all dolphins are members of the porpoise family.
 Bacon is not a vegetable.
 I'm not kidding.