1/4 cup butter or margarine, softened
1/4 cup mayonnaise
3 tablespoons Creole mustard
1 tablespoon grated onion
2 teaspoons poppy seeds
8 hamburger buns, split
1 (6-ounce) package Swiss cheese slices
1 pound thinly sliced ham
Combine first 5 ingredients; spread evenly on each bun half. Layer 8 bun halves evenly with cheese and ham; top with remaining halves. Wrap in aluminum foil; freeze.
Bake, frozen in foil, at 350° for 1 hour or until thoroughly heated.