Preheat your skillet or grill pan over medium heat and melt the butter, allowing it to sizzle gently and turn slightly golden.
Slice the slider buns in half horizontally, keeping the top and bottom connected, and spread a thin layer of Hawaiian sweet mustard on the inside of each bun.
Layer slices of honey-glazed ham on the bottom halves of the buns, making sure to cover evenly for a juicy, savory base.
Place pineapple slices on top of the ham, and if you like, add thin slices of red onion or jalapeños for a spicy or sharp contrast.
Close the sliders with the top bun halves, then brush the outsides lightly with the melted butter using a silicone brush, preparing them for toasting.
Place the sliders in the hot skillet or on the griddle, pressing gently with a spatula, and cook for about 2-3 minutes per side until the buns are golden and crispy, and the filling is heated through.
Remove the sliders from the heat and let them rest for a minute, allowing the juices to settle and the flavors to meld.
Sprinkle chopped cilantro or green onions on top for a fresh burst of flavor and serve immediately while warm and caramelized.