1. Cut mushrooms into thin slices; set aside. Dice celery. Finely chop green onion.
2. In 2-quart saucepan over medium heat, in 1 tablespoon hot butter or margarine, cook celery and green onion until tender, stirring occasionally.
3. Preheat oven to 350°F. Into medium-sized bowl, tear bread into small pieces. Add ground beef, catchup, egg, celery mixture, and 1/2 tea spoon salt; mix well. Shape meat mixture into a loaf about 4 1/2 by 2 1/2 place in 8" by 8" baking pan. Bake meat loaf 35 minutes.
4. Meanwhile, in same 2-quart saucepan over medium heat, in 1 tablespoon hot butter or margarine, cook mushrooms until tender, stirring occasionally. Stir in flour, paprika, and 1/4 teaspoon salt until blended; cook 1 minute. Gradually stir in milk; cook, stirring constantly, until mixture thickens and boils; boil 1 minute. Remove saucepan from heat.
5. Prepare noodles as label directs; drain.