For the sauce:
1½ tbsp. yellow mustard (I like to use Honey Dijon)
8 tbsp. butter, melted
1 tbsp. finely minced onion (or 2 tsp. dried minced onion)
½ tsp. Worcestershire sauce
Poppy seeds, for sprinkling
Preheat the oven to 350˚ F. Split the slider rolls and spread the insides lightly with mayonnaise. Fold a slice of ham to fit on each slider bun, and top with a slice of Swiss cheese. Replace the top bun to assemble the sandwiches. Place the sandwiches on a baking sheet.
To make the sauce, combine all ingredients except the poppy seeds in a small bowl and whisk to combine. (Sauce is almost all the way mixed, just add the melted butter). Drizzle the sauce over the tops of the slider buns. Sprinkle with poppy seeds. Cover with foil and bake 10 minutes, until the cheese is melted. Remove the foil and bake 2 minutes longer. Serve warm.
Serve with Frozen Peas