Take 1 large loaf of French or Italian bread and cut it in half length wise. Hollow out each half like a canoe, leaving 1/4 to 1/2-inch thickness to the shell. Put the bread that you removed into a large mixing bowl. Add ground beef, egg, mustard, evaporated milk, soda crackers, salt, onion and cheese. Mix together by hand as if you were making a meatloaf and fill both bread shells.
Preheat oven to 350-degrees. Place the filled shells on aluminum foil and pinch the foil together over the top of the filling, sealing them for baking. Bake for 30-40 minutes.
Remove from oven and open the foil carefully and cut through the middle of one half to make sure the meat is done to your liking. If not quite done, reseal, and place back in oven another 10-20 minutes.