brown ground beef in large skillet. Drain off fat. Sauté celery and green pepper two minutes. Stir in macaroni and sauce mix for Main dish, hot water and mustard. Heat to boiling. Stir constantly. Lower heat, simmer uncovered five minutes.
Mix the baking mix in cold water in small bowl. Beat 20 strokes. Pour beef mixture into an 8 cup casserole. Drop dough by tablespoons onto beef mixture. Bake in 450° oven for 15 minutes or until biscuits are Golden. Serves four.