Step 1

In a large skillet over medium heat, melt butter. Add onion and cook 5 minutes. Stir in mustard, Worcestershire sauce, and poppy seeds and cook about 10 minutes, or until onions are soft.

Step 2

Preheat oven to 350 degrees F.

Step 3

Slice rolls in half all at once and place bottom half in a 9- x 13-inch casserole dish. Spread 3/4 of onion mixture over rolls; top with ham, cheese, and top half of buns, then top with remaining onion mixture. Cover with aluminum foil.

Step 4

Bake 15 to 20 minutes or until heated through. Remove from oven, and slice down between the rolls to make individual sliders.