Brush the tops of the buns generously with the melted butter, making sure to get into the corners and along the edges so they toast up golden and flavorful.
Cover the sliders loosely with a second sheet of foil, tenting it slightly so it doesn’t stick to the cheese. Bake in the preheated oven for 10 minutes.
Remove the top foil and continue baking for another 5–8 minutes, or until the tops of the buns are lightly toasted and the Swiss cheese is fully melted and gooey.
Let the sliders rest on the baking sheet for 2–3 minutes so they’re easier to handle. Using a sharp knife, cut along the bun lines to separate into 12 individual sliders. Serve warm straight from the tray.
Variations & Tips
If you grew up stretching what you had in the fridge, this recipe is very forgiving. You can swap the Swiss cheese for provolone or a mild cheddar if that’s what you have on hand, though Swiss will give you that classic deli flavor. For a touch more richness, mix a teaspoon or two of prepared mustard into the melted butter before brushing it over the tops, or brush the cut sides of the buns with mustard before layering the corned beef—just keep in mind that would sneak in an unofficial “fifth” ingredient. If you like a crisper top, bake the sliders uncovered for the last few minutes under the broiler, watching closely so they don’t burn. These reheat nicely: wrap leftovers in foil and warm in a 325°F oven until heated through. For smaller households, make half a batch in a loaf pan but still line it with foil for that easy lift-and-serve cleanup. And if your corned beef is leftover from a boiled dinner, just slice or shred it thinly and use it in place of deli meat; the flavor will be a little homier and extra nostalgic.
