Cut steak into thin strips. Saute the strips in lots of butter with chopped onion, mushrooms, garlic powder, salt and pepper, MSG (if desired) and sherry. Butter a shallow baking dish. Cut the crusts from several sliced of bread (about one slice per serving). Butter both sides of the bread and put into the dish. Fill in the spaces with the crusts. Pour the steak over the bread and cover with sliced mozzarella cheese. Bake uncovered at 325 degrees for about 25 minutes.