Hot Ham 'n' Cheese

250 g butter or margarine, softened
150 g horseradish mustard
100 g finely chopped onion
30 g poppy seeds
8 french sticks or 40 dinner rolls
40 slices fully cooked ham
40 slices Swiss cheese
In a bowl, combine the butter, mustard, onion and poppy seeds. Spread over cut sides of buns. Layer ham and cheese on bottom halves; replace tops. Wrap each sandwich in foil; place on a baking sheet. Bake at 350 degrees for 25-30 minutes or until cheese is melted.