Description
These Buttery Roast Beef Sliders with Caramelized Onions are a decadent and savory treat perfect for any occasion. Featuring tender deli roast beef layered with melty cheeses, sweet caramelized onions, and a rich garlic aioli, all nestled in soft slider buns brushed with a flavorful garlic butter sauce. Served with a warm homemade au jus for dipping, these sliders deliver a gourmet twist on a beloved classic.
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
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 the butter and olive oil in a large skillet over medium-low heat. Add the sliced onions, sprinkle in the kosher salt and brown sugar, and cook low and slow, stirring occasionally, until the onions become soft, deep golden brown, and jammy — about 45 minutes. Stir in the beef broth at the end to deglaze the pan and incorporate all the flavorful bits. Set aside.
- Prepare 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 whisking, slowly stream in the oil until the mixture thickens into a creamy aioli. Season with kosher salt to taste and set aside. For a quicker variation, mix these ingredients into mayonnaise instead.
- Make the Au Jus Sauce: In a medium saucepan over medium heat, melt the butter. Stir in the Better than Bouillon beef base, beef broth, and Worcestershire sauce. Let the mixture simmer gently for 20 minutes until it reduces by about half, darkens slightly, and thickens a little as it cools. Keep warm for serving.
- Toast the Bottom Buns: Preheat the oven to 350°F (180°C). Slice the slider buns in half horizontally without separating the pairs. Arrange the bottom halves on a parchment-lined baking sheet, cut-side up. Lightly brush them with melted butter or garlic aioli and toast in the oven for 5 minutes until just golden.
- Assemble the Sliders: Spread a generous layer of garlic aioli over each toasted bottom bun. Pile the roast beef evenly over the buns in 2 to 3 layers for hearty sliders. Then place a slice of melty cheese on each, followed by a sprinkle of shredded mozzarella for extra meltiness. Spoon an even layer of caramelized onions over the cheese.
- Top and Prepare for Baking: Place the top half of the slider buns on each assembled slider. In a small bowl, combine the melted butter, Worcestershire sauce, poppy seeds, sesame seeds, garlic powder, dried minced onion, kosher salt, and freshly cracked black pepper. Generously brush this garlic butter mixture on the tops of the sliders.
- Bake the Sliders: Cover the slider pan loosely with aluminum foil and bake for 10 minutes. Remove the foil and bake for an additional 10 minutes or until the tops are golden brown and the cheese is melted and bubbly.
- 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, skip caramelizing the onions and simply jazz up mayonnaise with the aioli ingredients; bake the sliders without onions for a simpler roast beef slider.
- Make sliders up to two days ahead without the caramelized onions or garlic butter. Add these toppings and bake just before serving for the freshest result.
- Store leftovers in an airtight container in the refrigerator for up to 3 days.
- Reheat leftovers in the oven at 375°F for about 10 minutes to avoid sogginess and keep sliders fresh.
- Use Hawaiian rolls for the softest and sweetest slider buns, but any slider bun will work.
- The au jus can be kept warm on low heat or reheated gently before serving.
Nutrition
- Serving Size: 1 slider
- Calories: 320 kcal
- Sugar: 3 g
- Sodium: 520 mg
- Fat: 20 g
- Saturated Fat: 9 g
- Unsaturated Fat: 9 g
- Trans Fat: 0 g
- Carbohydrates: 22 g
- Fiber: 1 g
- Protein: 15 g
- Cholesterol: 65 mg
