Description
These Buttery Roast Beef Sliders with Caramelized Onions are a deliciously hearty and flavorful appetizer or main course perfect for gatherings. Featuring tender roast beef layered with melty cheese, sweet caramelized onions, and a rich homemade garlic aioli, all nestled in buttery toasted slider buns and served with savory au jus for dipping.
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 (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
- Freshly cracked black pepper, to taste
Instructions
- Make the Caramelized Onions: Melt butter and olive oil in a large skillet over medium-low heat. Add sliced onions, kosher salt, and brown sugar, then cook low and slow, stirring occasionally until onions are soft, deep golden brown, and jammy, about 45 minutes. Stir in beef broth to deglaze the pan and set aside.
- Make the Garlic Aioli: In a small bowl, whisk egg yolk, Dijon mustard, grated garlic, and lemon juice until smooth. Slowly stream in oil while whisking or blending until the mixture thickens into creamy aioli. Season with salt and set aside. For easier version, mix garlic, mustard, lemon juice, and salt into mayonnaise.
- Prepare the Au Jus Sauce: Melt butter in a medium saucepan over medium heat. Stir in beef base, beef broth, and Worcestershire sauce. Simmer gently for 20 minutes until reduced by half and slightly thickened. Keep warm for serving.
- Toast the Bottom Buns: Preheat oven to 350°F (180°C). Slice slider buns in half horizontally without separating. Place bottom halves cut-side up on a parchment-lined baking sheet. Lightly brush with melted butter or aioli and toast in the oven for 5 minutes until golden.
- Assemble the Sliders: Spread garlic aioli over toasted bottom buns. Pile roast beef evenly (2–3 layers) over the buns, then place cheese slices on top. Sprinkle shredded mozzarella over the cheese, followed by an even layer of caramelized onions.
- Top and Bake the Sliders: Place top halves of buns on sliders. In a small bowl, mix melted butter, Worcestershire sauce, poppy seeds, sesame seeds, garlic powder, dried minced onion, salt, and pepper. Brush generously over tops. Cover loosely with foil and bake for 10 minutes. Remove foil and bake another 10 minutes until tops are golden and cheese is melted.
- Serve: Slice between rolls to separate sliders. Serve warm with au jus sauce in small bowls for dipping.
Notes
- For a faster version, use mayo mixed with aioli ingredients and omit caramelized onions, baking sliders directly for about 30 minutes.
- Make sliders up to two days ahead without onions and garlic butter on a rimmed baking sheet, then add before baking.
- Store leftovers in an airtight container for up to 3 days.
- Reheat leftovers in the oven at 375°F for 10 minutes to prevent sogginess.
Nutrition
- Serving Size: 1 slider
- Calories: 320 kcal
- Sugar: 3 g
- Sodium: 580 mg
- Fat: 19 g
- Saturated Fat: 9 g
- Unsaturated Fat: 8 g
- Trans Fat: 0 g
- Carbohydrates: 22 g
- Fiber: 1 g
- Protein: 15 g
- Cholesterol: 65 mg
