1 lb. ground beef
2 (8 oz.) cans tomato sauce
1 tsp. oregano
2 c. Bisquick
1 egg
2/3 c. milk
8 slices American cheese
1 can mushrooms, drained
1/4 c. Parmesan cheese

Brown ground beef and drain. Mix in 1 can tomato sauce and oregano; simmer uncovered 10 minutes; stir together baking mix, egg, and milk; spread half of the batter in a greased 9 x 9 x 2 inch pan. Pour rest of tomato sauce over batter; layer 4 slices cheese, beef mixture, mushrooms, remaining cheese slices and Parmesan cheese. Cover with remaining batter. Bake 20-25 minutes at 400 degrees.