Cook and drain broccoli. Place in greased casserole. In pot, combine butter and flour thoroughly. Add milk gradually, stirring. Bring mixture to a boil; continue stirring. Reduce heat. Sprinkle with 1/2 t. salt. Cook for 1 minute longer. Add cheese; cook until cheese melts. Pour over casserole. Top with crumbs. Bake at 325 for 25-30 minutes. Garnish with paprika.