Preheat oven to 350 degrees F. Prepare a large baking sheet lined with aluminum foil. I like to form a container of sorts with the foil; folding it up so that it surrounds the rolls and contains any of the sauce that might drip. Split rolls in half; I use a large bread knife and since I use the King's Hawaiian Rolls, I simply slice the entire top as one piece and replace it after topping the bottom halves with all of the other components. Melt butter in a small saucepan; add the onion and simmer for 2-3 minutes until the onion has softened. Remove from heat and add the brown sugar, mustard, Worcestershire sauce and poppy seeds. Drizzle 1/4 of the butter mixture over the bottom section of rolls. Top bottom halves with ham; 2 pieces of bacon and Swiss cheese and place the tops back on the rolls. If you are using separated rolls, place them very close together on backing sheet surrounded by foil. Pour reminder of butter mixture over rolls; let sit for 10 minutes to allow the mixture to soak in a bit. Cover the rolls with foil and bake for 20-30 minutes or until the cheese has melted. Uncover and cook for 2-4 additional minutes until tops are slightly brown and crispy. Serve warm.