It is important to use stale bread in this recipe; otherwise too much liquid will be absorbed and the mixture will not blend together well.
Soak the stale rolls in warmed milk and squeeze out. Combine the rolls with meats, eggs, and seasonings, and mix well. Peel onions, leaving them whole, and simmer for 20 minutes. Trim the ends, scoop out the centers carefully, and chop the center portion before adding to the meat stuffing. Grease a baking pan with the butter. Stuff the onions and place them in the pan. Sprinkle with crumbs and cheese, and pour stock over the top. Bake for 30 minutes in a 350 degrees F oven.