Spread the bread slices with butter and cut into cubes. Place 1/3 of the cubes in a 2 quart casserole dish and sprinkle with 1/3 of the cheese; repeat 2 more layers. In a medium bowl beat eggs with milk, mustard, Worcestershire, salt and paprika. Pour over bread and cheese layers. Cover the dish and chill for at least 3 hours.
Preheat oven to 350 degrees F (175 degrees C).
Uncover the dish and bake in preheated oven for 1 hour. Let stand for 10 to 15 minutes before serving.