Hot Ham and Swiss Sandwiches

I swear my husband, Brent and I eat this dish every other week (used to be every week).  It's so easy to make the night before, pop it in the fridge and then put it in the oven the next day for dinner.  This recipe comes from my cousin Kim and it is a favorite among pretty much everyone!  Great weekday meal!  I cut everything in half or even just make 4 rolls.

Hot Ham & Swiss Sandwiches
Ingredients:
12 plain top hamburger buns or smaller
1-1.5lbs shaved ham
12 slices of swiss cheese
Sauce:
4 tablesppons brown sugar
1 tablespoon poppy seeds
2 tablespoons dry mustard
2 tablespoons Worcestershire sauce
1 stick of butter
Directions:
Spray 13x9 pan with Pam.  Make the ham sandwiches and place in pan.  Combine all of the sauce ingredients and bring to a boil, stirring.  Pour sauce over the buns.  Cover with aluminum foil and refrigerate overnight.  Bake, covered at 350 degrees for 25 minutes.  Take foil off and back an additional 5 minutes