Preheat oven to 350 degrees F. Lightly coat a 9x13 baking pan with nonstick cooking spray.
Place 12 (3-inch) pretzel roll bottoms in the pan. Spread with 1/2 cup Thousand Island dressing.
Top the rolls with 2 cups shredded cabbage.
Top the cabbage with 1 pound thinly sliced corned beef.
Top the corned beef with slices of Swiss cheese.
Place roll tops on top.
Whisk together the 5 tablespoons melted butter, 1 tablespoon mustard, and 2 teaspoons minced dried onion. Pour butter mixture over the sliders.
Cover with foil and bake in the oven for 30 minutes.
Serve hot with some chips and dill pickles and enjoy!
Notes
The cabbage can easily be replaced with sauerkraut, but use about half the amount and make sure you ring out all the liquid or the sliders could get soggy.