Thinking about medieval food brings up the subject of New World introductions: a fairly large percentage of what we -- Europeans and North Americans -- normally eat originated in the Americas. To see how large, let's look at some common menus.
Breakfast first. Bacon, eggs, and toast are on firm ground: the ingredients, if not the manner of preparation, were available in 6th century Britain. Oatmeal porridge with milk or cream is also safe. Cornflakes, however, are right out: maize is New World.
Lunch is a bit more of a problem. Hamburgers are fine, as long as you leave off the (tomato based) catchup, but you can't have fries with them. Potatoes are New World. Salad greens are mostly safe, and so are cucumbers, but again no tomatoes. Olive oil and vinegar are Mediterranean, and garlic. So are most pizza ingredients, if you leave off the (tomato) sauce.
And so to dinner. Contemporary feasting, like its medieval counterpart, includes large cuts of meat. Beef, pork, lamb, and chicken are no problem. Turkey is North American, as some of us notice every November. As I've already said, no potatoes, no tomatoes, no corn on (or off) the cob, and definitely no baked beans (all our beans except fava beans and related broad beans are New World). Rice was Old World, though probably not available in 6th century Britain, and the ingredients for pasta were there, though again probably not the thing itself. Beets and turnips are European. Many if not most hot peppers are originally New World; so are sweet peppers. Pumpkin or blueberry pie wasn't available, but apples, strawberries, dates and almonds have all been found in Roman deposits. The Romans had plenty of wine, and the Celts and Germans made beer in great quantity, but there was no tea or coffee in medieval Europe -- and definitely no chocolate!