Preheat oven at 375 degrees.
Prepare ducks. Filet duck breasts. Slice each filet in half to make 2 thin steaks. Combine flour, onion salt and garlic salt. Dip filets in seasoned flour. Brown in butter in skillet. Place in shallow casserole dish. Saute onion and mushrooms in pan drippings. Add tomato sauce, spaghetti sauce mix, parmesan cheese and 1/4 cup parsley. Cook covered for 15 minutes, stirring occasionally. Pour over filets. Combine Mozzarella and Cheddar cheeses. Sprinkle over casserole. Top with remaining 1/4 cup parsley. Bake covered until cheese