I'd open a gruel restaurant! The menu would list various types of gruel, porridge (such as pease porridge, available hot or cold, though not actually nine days old), oatmeal, polenta, bread pudding, cereal, etc. The customers would sit on rough-hewn wooden benches at rough-hewn wooden tables, and eat out of rough-hewn wooden bowls with rough-hewn wooden spoons. The waiters would be dressed like that guy from "Oliver Twist" who says, "MORE?!?"
Ooo, or how about a comfort-food restaurant? There'd be peanut butter & jelly sandwiches, tomato soup, doughnuts, Cheetos, cereal, stuff like that. And big-screen TVs showing cartoons.