Layer ham and cheese on the bottom half of each pretzel bun, and place the top half on top.
Place the sandwiches in a 9 x 13 inch pan. They will fit tightly.
Melt the butter.
Add the diced onion, mustard, and honey to the melted butter and stir well.
Pour the butter mixture over the top, distributing it evenly over each of the sandwiches.
Sprinkle the poppy seeds over the sandwiches.
Cover tightly with foil and bake for 20-30 minutes until warmed through and bubbling.
Remove foil and serve immediately
You can make these amazing sandwiches on Hawaiian rolls, onion buns, or even regular hamburger buns. If you use a larger bun, it will make 8 sandwiches.You could also substitute dried minced onion for the fresh diced onion. But use half the amount.