Description
Buttery Roast Beef Sliders with Caramelized Onions are savory, melty mini sandwiches perfect for gatherings or a hearty snack. Featuring slow-cooked caramelized onions, homemade garlic aioli, and a rich au jus sauce, these sliders are baked to golden, cheesy perfection with a flavorful garlic butter glaze.
Ingredients
Scale
Caramelized Onions
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 3 large yellow onions, thinly sliced
- ½ teaspoon kosher salt
- 1 teaspoon brown sugar
- 2 tablespoons beef broth
Homemade Garlic Aioli
- 1 large egg yolk, room temperature
- 1 teaspoon Dijon mustard
- 1 garlic clove, finely grated or minced
- 1 tablespoon fresh lemon juice
- ½ cup light olive oil or neutral oil
- Kosher salt, to taste
Au Jus Sauce
- ¼ cup unsalted butter
- 1 tablespoon Better than Bouillon Beef Base
- 2 cups beef broth
- 2 teaspoons Worcestershire sauce
Roast Beef Sliders
- 12 slider buns, sliced in half (Hawaiian rolls, preferred)
- ¼ cup homemade garlic aioli or mayonnaise
- ½ pound deli roast beef, thinly sliced
- 12 slices melty cheese, like provolone, Swiss, or muenster
- ½ cup shredded mozzarella cheese
- 2 cups caramelized onions
Garlic Butter Sauce
- 6 tablespoons unsalted butter, melted
- 1 teaspoon Worcestershire sauce
- 1 tablespoon poppy seeds
- 1 tablespoon white sesame seeds
- ½ tablespoon garlic powder
- ½ tablespoon dried minced onion
- ½ teaspoon kosher salt and freshly cracked black pepper
Instructions
- Make the Caramelized Onions: Melt the butter and olive oil in a large skillet over medium-low heat. Add the sliced onions, sprinkle in the salt and brown sugar, and cook low and slow, stirring occasionally, until the onions are soft, deep golden brown, and jammy — about 45 minutes. Stir in the beef broth at the end to deglaze the pan and pick up all that good flavor. Set aside.
- Make the Garlic Aioli: In a small bowl, whisk together the egg yolk, Dijon mustard, grated garlic, and lemon juice until smooth. While blending with an immersion blender or using a whisk, slowly stream in the oil until the mixture thickens into a creamy aioli. Season with a pinch of salt and set it aside. (If using mayo instead, just stir in the garlic, mustard, lemon, and salt.)
- Get the Au Jus Started: Melt the butter in a medium saucepan over medium heat. Stir in the Better than Bouillon beef base, beef broth, and Worcestershire sauce. Let it simmer for 20 minutes until it reduces by about half. It will darken slightly and thicken a little as it cools. Keep warm for serving.
- Toast the Bottom Buns: Preheat the oven to 350°F. Slice the buns in half horizontally without separating them. Place the bottom buns, cut-side up, on a parchment-lined baking sheet. Brush lightly with melted butter or aioli and toast for 5 minutes until just golden.
- Assemble the Sliders: Spread a generous layer of garlic aioli over the toasted bottom buns. Pile the roast beef evenly over the buns in 2–3 layers. Lay down your slices of cheese, then sprinkle the shredded mozzarella over the top for extra meltiness. Spoon an even layer of caramelized onions across the sliders. Place the top half of the rolls on the sliders.
- Prepare the Garlic Butter Sauce and Bake: In a small bowl, mix together the melted butter, Worcestershire sauce, poppy seeds, sesame seeds, garlic powder, dried minced onion, salt, and black pepper. Generously brush the tops of the rolls with the garlic butter mixture. Cover loosely with foil and bake for 10 minutes. Remove the foil and bake for another 10 minutes until the tops are golden brown and the cheese is melty.
- Serve: Slice between the rolls to separate the sliders. Serve warm with little bowls of au jus on the side for dipping.
Notes
- For a quicker 30-minute version, use mayo mixed with garlic, mustard, and lemon instead of making aioli, and bake sliders without caramelized onions.
- Make sliders up to two days ahead without caramelized onions or garlic butter; add them just before baking.
- Store leftovers in an airtight container for up to 3 days.
- Reheat leftovers in the oven at 375ºF for about 10 minutes to avoid sogginess.
- Use Hawaiian rolls for best slider texture and flavor.
