These French dip sliders are the perfect party food. Made with thinly sliced roast beef, melty Swiss and provolone cheeses, caramelized onions, and homemade au jus, they're a total crowd pleaser!
Melt 2 tablespoons of butter in a skillet over medium heat. Add the sliced onions and season with salt and pepper. Cook, stirring frequently, until golden and caramelized. Remove all but 2 tablespoons of the onions to a bowl and set aside.
Add remaining butter and beef broth to the skillet. Bring to a simmer over medium-high heat, then reduce the heat to medium-low and allow to simmer for about 10 minutes, or until the liquid is reduced by almost half.
Preheat oven to 350°F. Coat a 9 x 13 baking dish with non-stick cooking spray and set aside.
Use a serrated knife to cut the entire sheet of slider buns in half through the middle to separate the top of the buns from the bottom of the buns. Place the bottom halves in the baking dish.
Top buns with the reserved onions, Swiss cheese, roast beef, provolone cheese, and slider bun tops.
Melt the remaining butter and optional Worcestershire sauce in the microwave or a small saucepan over medium heat. Brush on the tops of the buns.
Cover the casserole dish with foil and bake for 20-25 minutes, or until the cheese is melted and the sandwiches are warmed through.
Serve sliders with the homemade au jus for dipping.
Notes
Leftover sliders can be refrigerated in an airtight container in the refrigerator for 1-2 days. Reheat sliders in the microwave or cover them with aluminum foil and bake until warmed through.Wrap in foil then place in a freezer baggie to freeze for up to 2 months.