Italian Cresent Casserole

1lb. ground beef
1/4 cup chopped onion
1 cup spaghetti sauce
1 1/2 cups mozzarella cheese, shredded
1/2 cup sour cream
1 tube refrigerated crescent rolls
1/3 cup Parmesan cheese, grated
2 Tbsp butter or margarine, melted

Preheat oven to 375 degrees. Brown meat and onion in large skillet.
Drain. Add spaghetti sauce; heat through. Pour meat mixture into 12x8
inch baking dish. In small bowl, combine sour cream and mozzarella
cheese. Spoon over meat mixture. Unroll dough and cover meat and
cheese mixture (stretching and spreading as necessary).Combine
Parmesan cheese and butter; spread evenly over dough. Bake at 375 for 18-25 minutes or until golden brown.