Begin by preheating your oven to 180°C (350°F) and lining a baking sheet with parchment paper. Slice the slider buns horizontally, keeping them attached on one side if possible, and set aside.
In a small saucepan, combine honey, Dijon mustard, and melted butter. Warm over low heat, stirring gently until the mixture is smooth, fragrant, and slightly runny, about 2 minutes.
Spread a generous layer of the honey mustard glaze on the cut sides of the buns using a basting brush. Cover the surface evenly to infuse lots of flavor and help with browning.
Lay slices of leftover ham evenly on the bottom half of the buns. If using cheese, layer a slice of sharp cheddar over the ham for extra meltiness and flavor.
Place the top halves of the buns back onto the layered fillings, pressing down gently. Then, brush the outside of the buns lightly with the remaining honey mustard glaze for a shiny, sticky finish.
Arrange the assembled sliders on your prepared baking sheet. Cover loosely with foil and bake in the preheated oven for 10-12 minutes, until the cheese is melted and the buns are golden brown with a slight crisp on the edges.
Remove from the oven and let the sliders rest for 2 minutes. This allows the cheese to set slightly and the flavors to meld. Serve warm, optionally with extra honey mustard or your favorite toppings.
