In many ways, period food is just like modern food. In other ways it’s spectacularly different. There were many more foods to choose from, even though more food was locally (and organically) grown. Social class made a huge difference in the kinds of foods one could eat, and the prevalent Christian religion enforced a type of vegetarian diet for a good part of the year. The medieval feast could outdo the most expensive restaurant in presentation of vittles.
Here are some sources to help start your food research: Books | Web Pages