One of my characters (who comes from Earth) wants to open a restaurant in a fantasy world. This world is currently in its medieval era.
The restaurant would serve all sorts of modern food; deep fried, baked, you name it and they have it. The restaurant is equipped with modern kitchen appliances and facilities.
Given medieval farming and food preservation techniques, is it possible to create foods like we have now with the available ingredients?
Considering @In the name of the story’s update that the protagonist has modern refrigeration and transportation available to him/her/them, the only barrier should be the fact that many food ingredients would not be available in the place where the restaurant would open in. Assuming that the restaurant will open in Medieval Europe (as that’s what most people think of when they refer to the medieval era), the only ingredients available to the protagonist would be those locally available.
Let’s say that the restaurant opens in medieval England and the protagonist wants to serve the following foods:
Here’s how it would turn out:
There was no refrigeration in the Middle Ages. So ingredients had to either be sourced locally, or preserved in some way. So no fresh oranges in Stockholm, for example.
The next problem you have is that some ingredients haven't been invented yet. Just as an example, look at all the different kinds of pepper the hot pepper community has invented in it's race to have the hottest pepper.
Next, many ingredients have changed quite a bit since the Middle Ages. Fruits and veggies have pretty much all been bred to be larger, and in many cases more flavorful. Livestock have been bred to produce meat with specific marbling qualities. Essentially you're missing out on ~600 years of artificial selection. One example of an ingredient you miss because of this would be Kobe Beef, but there are others.
Last, some ingredients were only found in the New World. Tomato, potato, and chocolate to name a few.
With all this in mind, some recipes would be possible, while others wouldn't. Exactly what is available depends on exactly where you are.
I suggest making your restaurant an ice cream parlor.
Most modern food preparation techniques were used in the middle ages. They did not have microwaves, but steaming or putting something to stand near the fire could get similar results, just slower. It was certainly possible to create foods similar to modern ones if the ingredients were available. To see the variety of dishes that were actually prepared I suggest reading some medieval cook books.
The big difference is that the ingredients for modern cooking were either not available, or too expensive for most people to eat them. The people who could afford the quantities of protein (especially beef), refined white flour, spices, and sugar would eat at the high table in their own hall, not at an inn or tavern. A medieval celebrity chef worked for a VIP, rather than opening restaurants.
A few wealthy people in the right areas might be able to have ice brought from a mountain glacier, but most people in most areas had no access to frozen dishes if it was warm enough to make them enjoyable.
Fermented fruit juices, milk, eggs, and honey were all reasonably available at prices a merchant could afford, at least in small quantities as a treat. If you did your buying quickly, at the right time, you might even be able to get unfermented fruit juice into your freezer. It is sweeter, and freezes better. Cook everything to kill bacteria before freezing.
Based on some comments on another answer, the ice cream parlor could also offer, based on distillation, completely clear, safe drinking water with ice in it.
There were no restaurants as such in medieval Europe (just odd bakeshops and vendors for working types who could not get home to eat). The concept was quite alien to them. You would have to work extremely hard to build any sort of clientele -- those with the money would much rather be in their own grand homes, those without cannot afford to eat there.
That, and getting people to eat strange foods, is going to be a huge challenge. It took a long time even for things like Chinses and Indian cuisine to catch on in the West.
Far better to get employed as the personal chef of a king or noble and become famous for hosting the most amazing feasts.
((BTW a not totally dissimilar concept appears in my own War of the God Queen when a 19th-century Frenchwoman timeslipped to the Bronze Age decides that the locals need the civilising effects of proper cookery and makes the most of local ingredients))
There hasn't been a lot of innovation in cooking techniques, and preservation is mostly needed to have things year-round rather than in-season. The big difference is transportation. We take for granted meals combining ingredients that don't grow within a thousand miles of each other.
If you're attempting to recreate modern american food in medieval Europe, what you'll most miss is tomatoes. Unless you're specializing in desserts, in which case chocolate.
You'll also routinely wish for refined sugar, which exists in India and theoretically could be imported, but AFAIK never was. Honey and boiled pear juice are all available, though expensive and not quite the same.
Spices should be pretty available, albeit expensive. (Also, no allspice, vanilla or chili peppers.) A lot of them have to be imported from India, but those trade routes exist.
But in a fantasy world with medieval technology, you can decide what plants they have within their trade network. Including they could all be different plants, and your hero has to methodically eat one leaf or berry after another thinking "this can kind of substitute for that"...
I think we're looking at this wrong... The thing to do is bring some of your own produce (stuff that can be grown locally) and focus on culinary traditions that would be unfamiliar to the area.
I'm going to assume you're in England (partly because they are notorious for poor cuisine) for my examples, but similar ideas should apply anywhere. Simply serving period French or Spanish cuisine here would be noteworthy, and you have a better chance of being able to get the ingredients. Introducing tomatoes or possibly pasta would be huge. Asian fare (Chinese, Japanese, Indian) would be even better, but getting the spices may be challenging, or at least prohibitively expensive. Instead, you might try introducing cilantro and making New World.
You mentioned baking. People of the area already knew how to bake meat pies. You might be able to wow them with sheer artistry, but without sugar, "baking" isn't going to be much like our modern notions of "pastry". (However, if you can introduce sugar beets, you will probably blow their minds. I'd suggest baklava, which uses honey, but I'd actually be surprised if something like that isn't already known.)
I mentioned forks in a comment. One area you might have some success is focusing on dishes that you really wouldn't want to eat with your hands and a knife or bread bowl. Corn already removed from the cob, shelled peas, salads, mashed potatoes, ragout... Most pasta or rice dishes might be good candidates, actually. Alternatively, introduce chopsticks 😉.
Introduce teppanyaki and/or "Mongolian Barbecue". There was already some culinary theater, but my impression was that it was reserved for the "upper crust" and was possibly wasteful of food and was more about the presentation than the cooking itself.
Site your restaurant in a seaport; and make friends with shipowners and sea captains. They eat free all year round, if they add a few sacks of rice, dried fruit or meats, or spices to their cargo, or (for only the fastest ships ... maybe favours from the Navy) fresh oranges from Seville or bananas (picked green) from West Africa.
Especially if they travel the length of the Mediterranean, let them know of fables you have heard of bitter beans from Ethiopia, and have them ask around the markets for caravans from the Red Sea. Ground up, they make a special drink, but keep that knowledge to yourself. (It's no accident that marine insurance started in a coffee house, run by Lloyds...)
