Some poor soul on tumblr was unfortunate enough to ask what would be appropriate for the Musketeers to eat, and I decided to whip up immediately kilometers of meta on the subject. I happen to have a lot of feelings about 17th century French cuisine (about food in general, but 17th century French cuisine in particular, because Cyrano de Bergerac is one of my favourite plays ever and act II opens basically with food porn for no reason and it's awesome).
17th century is precisely the time where French cuisine come out of the Middle Ages; it's a time of new techniques, new products, and general innovations. 17th century is the "Grand Siècle", the Great Century, and obviously it called for a Grande Cuisine too because hey, THIS. IS. FRAAAAANCE!!!! Before that time, there was virtually no cookbook published for centuries, and in that century one of the first great French cooks called La Varenne published "Le Cuisinier François" ("the French cook") which became a best-seller (and which kept being re-printed until 1815!). It's the very first cookbook that details rules and principles of cooking.
A REVOLUTION FROM MEDIEVAL (AND RENAISSANCE) CUISINE
To understand 17th century French cuisine, you have to understand how it's different from medieval cuisine first.
Medieval cuisine used lots of spices (in the nobility, mainly, but not in order to mask the dubious freshness of the meat like many people seem to think -- in fact meat in the Middle Ages arrived probably fresher in the kitchen than it does today; but because spices were expensive, and it showed you had a lot of money. Also spices were believed (turned out to be true) to have curative properties. Medieval cuisine is also loaded with sugar and honey, or sweet and sour taste; 17th century is where savoury makes a big come back and it's what cooks would call a "return to the product", where you don't try to mask its flavour with other stuff so much. Medieval cuisine hid the taste of the ingredients, 17th century (supposedly, at least it's the theory behind it) puts it forward and the visual quality of the dishes improve a lot too. Sugar is reserved for desserts from then on (see: cakes, at the end of this article). I'm a great fan of Chinese cuisine and I enjoy a lot of different styles of cuisine from all over the world, so it's funny to me how French cuisine is still kind of allergic to sweet and sour taste in a dish to this day; and most French people I know aren't very fond of it either.
COOKING TECHNIQUES, APPLIANCES AND INNOVATIONS
In the 17th century, people pay more attention to how meat is cooked so it gives out its full flavor. An ancestor to the gas stove is invented, called a "potager" (a "potager" can be in French a patch of land where you grow vegetables, but at that time it's also where you make a "potage", which is a vegetable soup) that worked with cinders (basically you put cinders -- taken from the chimney fire -- in it to heat it up and then you could put your pans on top of it). Daubes (meat cooked in a pan, generally with red wine, for a long time) and ragoûts (meat cooked with vegetables, again for a long time) become common place. There's also lots of roasted meat, cooked in the fireplace with a spit and a recipient called "lèche-frite" underneath to catch the dribbling cooked fat and juices (to be re-used in the sauce); the meats are cooked for a very long time. Fish, poultry, most meats were served whole; people spent a lot more time at the table eating than we do today.
SAUCES, CONDIMENTS AND VEGETABLES
Sauces are perfected too, in order to accompany meat, and fresh aromatic herbs replace the medieval spices: chervil, bay leaves, thyme, parsley (very popular, because also very decorative), chive, rosemary, tarragon. To give more flavour to the sauce you could also use the technique of reduction (wait for water to evaporize out of the sauce, which leaves a concentrated flavour behind) or make a jus, which is a kind of sauce that re-uses the juices escaped from the cooked meat to pour it back on top of it. In medieval times, sauces used to be thickened with bread; La Varenne replaced those bread sauces with roux (flour and butter added to broth) and he also replaced pig fat with butter; lots of eggs and cream were used too; so you can see that 17th century cuisine defined the bases of what we call French cuisine today.
Garlic is rejected by the aristocracy but can be consumed by lower classes (and is used in Gascony cuisine too). Smelling of garlic could indicate that you came from peasantry. Capers, anchovies and shallots are very appreciated; new vegetables are starting to be used (they have to be very fresh and harvested early): peas, asparagus, cucumber, cauliflower and artichokes. NO salads, and next to no vegetables are eaten raw (they even cooked cucumbers; stuffed them first then cooked them).
GASCONY CUISINE
D'Artagnan is a noble and, as they say in the show, a farm boy (those two notions are actually compatible at the time, not all nobles were powdered prissy people as the cliché would have it). He also comes from the South-West of France, he's a Gascon, and Gascons KNOW THEIR FOOD. So no, he wouldn't eat the ancient equivalent of mac and cheese and hot dogs; he may be young and single, and no matter his BBC portrayal or what they did with him in the American adaptations, a credible d'Artagnan would have been raised to eat GOOD SHIT. He would take pride in dishes and produce that come from his home region and dismiss other regions' variations on traditional recipes -- I have to remind you he's FRENCH, that kind of stuff is SRS BSNS to us, even (or maybe more so) in the 17th century. That doesn't mean he'll prepare them himself of course, I don't think he would know how to (although I think he must know how to kill and pluck a goose, duck or chicken, skin a rabbit or a deer, even milk a cow; he's a noble from the countryside, albeit not a rich one, he must have had a few servants but I can imagine that he and his father probably helped them out on the farm because they must not have had enough hands anyway -- BBC!d'Artagnan seems to have good knowledge of farm animals, or at the very least horses, if we remember the line about setting the horse to a canter pace in episode 3, so we can assume he's not afraid to get his hands in the dirt).
Gascony cuisine ("cuisine gasconne") is actually a very famous type of cuisine in French tradition throughout centuries; Gascony is the land of "bien-vivre et bien-manger" (good living and good eating). Today we know it as South-West cuisine, which is based, then and now, on duck/goose fat (in opposition to Provençale cuisine - South, South-East of France -- which uses mainly olive oil to cook, or Normandy cuisine (North-West of France), which cooks with butter). So lots of ducks and geese in Gascony cuisine, goose and duck confit (goose and duck cooked and preserved in their own fat), pâtés, terrines, sausages, foie gras, cured ham... Lots of venison, products of the hunt (mainly birds, like pigeons and larks).
Gascony is also near the sea so you also have sea food, like oysters, eel (eels were very appreciated, because their flesh is fat; they did love their eels pâté in those times)
And Gascons know their wine too. Not in a "Sideways" or connoisseur kind of way, you wouldn't see d'Artagnan tasting wine and say "oh yes I can smell raspberry and humus and there's a touch of vine leaves in it" or whatever so don't do that in your fanfics, it's not only OOC it's historically inaccurate (the kind of wine they drank in that day was not the kind of wine we drink today anyway, most of the time it had to be cut with water to be drinkable at all, otherwise it was just too thick or too strong); they just know what's *good* wine and what's not.
As for typical vegetables in Gascony, you have sweet pepper (piment doux de Gascogne), beans, a lot of very good and refined mushrooms like ceps and truffles; nave, onions, cabbage...
CAREFUL THOUGH, no tomatoes and no potatoes! Even though they were around, they were considered toxic at the time and weren't very much in use; so NO meat-and-potatoes menu!
So how do those Musketeers feed themselves if they want to eat good food (and not the one prepared by the cook in the musketeers barracks that we see in episode 4)? Well if they don't have a cook of their own, they eat in hostels, mainly, or they go to other people's places where they do have a cook (in the first book that's what the boys do when they're out of money: each one in turn, they call favours with (rich) friends of theirs to have dinner at their place, and they invite the other three guys of the gang along. D'Artagnan, being on his own in Paris, managed to find a Gascon priest and they apparently have teatime with chocolate at that priest's place)
LET THEM HAVE CAKE
Okay so if you ever want to read GLORIOUS food porn, read at least the beginning of Act II of the play Cyrano de Bergerac by Edmond Rostand, where one of the characters, Ragueneau, is a "maître-queux" (a cook and a pastry chef) and a poet (isn't he the MOST RAD CHARACTER EVER???). At Ragueneau's place, Rostand describes white peacocks (!!) on hooks, venison, hams suspended all around... and then begins a great choreography of sous-chefs bringing in piles of cakes: there's brioche (a type of sweet French bread made with butter, milk, sugar and eggs, very moist and delicious, sometimes perfumed with orange flower blossom essence), petits-fours, fruits in nougat, flan, roinsoles (fried pastries filled with fish or meat), tarts, pies, a big masterpiece of a brioche in the shape of a lyre (!!!), decorated with glazed fruits and its cords are made of spun sugar (Ragueneau rewards handsomely the sous-chef who brings him that work of art because Ragueneau is awesome like that), pâtés (pâtés designated either the meat terrines or puff pastries filled with meat and sauce, a bit like Cornish pastries), choux filled with cream, gingerbread, poupelins (a type of delicate pastry made with butter, milk, eggs, flour, sugar and lemon zest) and finally, the most famous of them all because Ragueneau composed a brilliant and adorable poem about them, "tartelettes amandines", almond-flavoured tartlets (if you ever put tartelettes amandines in your Musketeers fanfic, I WILL LOVE YOU FOREVER).
In the 17th century the art of jam-making (yes! An art! Absolutely!) is also born, which produced compotes (fruit purée), gelées (jelly) and marmelades. Tea, coffee and hot chocolate start to become fashionable drinks.
So there, I hope this will help you if you ever want to make dishes as an homage to our boys the musketeers, or if you want a spot of food porn in your fanfics, or just if you want to know more about the history of French cuisine; at least I can say I had a lot of fun researching and writing this :)