1. Preheat and Prepare: Preheat your oven to 350°F (175°C). Lightly coat a 9×13-inch baking dish with cooking spray.
2. Cook the Onions: In a saucepan over medium-low heat, melt the butter. Add the chopped onion and sauté, stirring occasionally, until the onions are soft and translucent, about 5 to 10 minutes. Stir in the mustard, poppy seeds, and Worcestershire sauce. Continue to cook and stir for another 5 minutes.
3. Prepare the Rolls: Place the bottoms of the rolls in the prepared baking dish. Spoon 2/3 of the onion mixture evenly over the roll bottoms.
4. Add Ham and Cheese: Layer the ham and cheese slices over the onion mixture on each roll. Place the roll tops over the cheese layer and brush the remaining onion mixture over the top of the rolls. Cover the dish with aluminum foil.
5. Bake the Sandwiches: Bake in the preheated oven for 15 minutes. Remove the foil and continue baking until the tops of the rolls are lightly browned, an additional 5 to 10 minutes.

Enjoy your delicious baked ham and cheese sandwiches with a flavorful onion topping! 🥪🧀🍴

½ cup butter

1 (12 count) package Hawaiian sweet rolls, split, or more as needed

1 onion, minced

1 pound sliced deli ham, or more as needed

1 tablespoon poppy seeds

2 teaspoons Worcestershire sauce, or more to taste

3 tablespoons Dijon mustard

8 slices Swiss cheese, or your preferred cheese

Cooking spray