Cook rice in double boiler. Add butter and salt. Mix lightly. Line well-oiled baking dish with rice. Pour tuna fish into rice mold. Cover with white sauce which has been combined with the egg. Bake in moderate oven (375 F) 30 minutes. Sprinkle with paprika. If desired, minced beef, chicken, or salmon may be used instead of tuna fish. 8 servings.