Place clams and liquid in medium saucepan and simmer 5 minutes.
Melt butter in small saucepan over medium heat. Add onion, green pepper, celery leaves, celery, pepper, salt and mustard. Cook until vegetables are tender-crisp. Add to clam mixture. Stir in crumbs and mix well.
Place in shells or ramekins. Sprinkle lightly with paprika. Bake at 450 F until nicely browned and bubbly, about 15-20 minutes.
Contributed by Joyce Taylor