Dwarves don't really have a system of "peasants" and "kings" like medieval (human) life, though. They live far more communally.
Besides that, [http://news.bbc.co.uk/2/hi/health/7148534.stm]the concept of a peasant eating nothing but porridge every day was a Victorian myth[/url], (
also,) they tended to eat more varied diets, at least outside of Winter. A peasant's dinner might be some bread, cheese, and a stew of some rabbit or fish they caught with garden vegetables or marinated in one of their orchard's lemon's juice with some herbs.
Anyway, I strongly back Jiri Petru's idea that "Dining Halls" or taverns are actually something more similar to a cafeteria. Real life, historical mead halls or taverns would have a menu of one or two different things, usually something like a stew or soup served from a big pot where they threw the day's ingredients in and let simmer while letting anyone who paid the entrance fee. These were not meals you packaged up and stored. Again, the idea would be that a kitchen "zone" might have a cauldron for a stew as a built furniture, from which hungry dwarves would take their meal. When empty, a cook would come and fill it back up.
Not everything that was "dine in" would necessarily be a stew or soup, of course, although it is more versatile as a cooking method, and roasted, sauteed, or fried foods would also be available. Frying foods was especially popular among the poorer, because it meant more calories for those who performed demanding, high-calorie labor like woodworking. Modern pigs are generally lean and bred for meat, but historically, were ludicrously obese, and bred for lard. Before vegetable oil was popular, it was how you greased the pan, it flavored food, it made good lamp oil, it sealed jars air-tight, made soap, etc.
For meals that would last a little while, so that someone might buy it as the equivalent of "take out dining", pies were quite common. A bakery could sell pies with nearly anything inside, and it would last for a few days so you could eat at home, although one could certainly dine-in with a pie, as well.
Real
preserved foods, meanwhile, would almost certainly be dried and salted meat/jerky/lutefisk, salty crackers and hard cheese. Pickles (vegetables) and jams (fruits) exist, but pots to contain them are bulky, and the major reason to eat this stuff was because you were on the road, so they wouldn't be preserved in large quantities outside of a few family stashes of jam or pickles for flavor through Winter. Regardless, it would invariably be preferable to eat a nice, warm,
fresh stew to ancient biscuits that you have to boil in lard to make soft enough that your teeth could actually win the fight against them.
I better stop here, though, because I might start down talking about nutrition models...