Cook beef, onion, green pepper and garlic in a large skillet until browned.
Drain; stir in red pepper flakes (op.) and spaghetti sauce and set aside.
In a large bow, mix spaghetti, Parmesan cheese, eggs and butter. Spread in a greased casserole dish; spread cottage cheese over the top. Pour sauce mixture over cottage cheese; and sprinkle with mozzarella cheese.