Grease a 9x13’’ dish with non-stick cooking spray. Set aside.

Assemble sandwiches: Slice the rolls in half horizontally and place the bottom halves in the baking dish. Layer 1-2 slices of ham and cheese on each roll and cover with roll tops.

Make sauce: In a small bowl mix together the melted butter, mustard, grated onion, and Worcestershire sauce. Spoon the sauce over the tops of the sandwiches. Allow rolls to rest for 10-15 minutes before baking, or refrigerate for up to 1-2 days (depending on how fresh your ingredients are).

Bake at 350 degrees F for about 15 minutes, or until warmed through and the cheese is melted.