12 buns (or less if large buns are used)
Mix well and spread on both sides of bun:
1/2 cup of softened butter
1 tablespoon finally chopped onion
1 tablespoon poppy seeds
1 tablespoon mustard
Add a slice or two of ham to the bun and a slice of Swiss cheese. Wrap sandwich in aluminum foil. Bake at 300° for 20-30 minutes.
For the buns, I like petite Kaiser rolls, and we place sliced onions on top of the ham and cheese instead of adding minced to the butter.