Brown ground beef in oil, stirring constantly.
Drain beef, then add tomato sauce, onion, parsley, Italian seasoning, bouillon cube, and garlic.
Heat to boiling, reduce heat, and simmer 20 minutes.
Cool 5 minutes.
Stir in cheeses, egg, and mushrooms.
Cut a 1 ½” horizontal slice off top of French bread loaf.
Remove center portion of bread, leaving 1″ sides of bread shell.
Put beef mixture in loaf and wrap in a large piece of buttered aluminum foil.
Bake at 300º for 30 minutes.
Remove foil.
If desired, sprinkle with ¼ cup shredded mozzarella cheese and return to oven for 5 minutes, or until cheese melts.
