01 - Preheat oven to 350°F. Line a baking sheet with parchment paper.
02 - In a small bowl, combine mayonnaise, Dijon mustard, and horseradish if using.
03 - Slice slider buns in half horizontally and arrange bottom halves on the prepared baking sheet.
04 - Spread the sauce mixture evenly over the bottom halves of the buns.
05 - Top each bun with corned beef, a spoonful of sauerkraut, and a slice of Swiss cheese.
06 - Place the top halves of the buns over the cheese.
07 - Brush tops with melted butter and sprinkle with caraway seeds and black pepper if desired.
08 - Cover loosely with foil and bake for 10 minutes. Remove foil and bake 5 minutes more until cheese melts and tops turn golden.
09 - Serve sliders warm.