Description
These Buttery Roast Beef Sliders with Caramelized Onions are a decadent and flavorful meal perfect for gatherings or a hearty snack. Featuring tender deli roast beef, melty cheese, homemade garlic aioli, rich caramelized onions, and buttery toasted slider buns brushed with a savory garlic butter sauce, these sliders are served with a warm au jus for dipping. This recipe balances slow-cooked sweetness in the onions with robust savory elements, offering a satisfying comfort food experience.
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 (such as 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 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 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 salt to taste and set aside. Alternatively, mix mayonnaise with garlic, mustard, lemon juice, and salt for a quicker version.
- Prepare the Au Jus Sauce: Melt the butter in a medium saucepan over medium heat. Stir in the beef base, beef broth, and Worcestershire sauce. Let it simmer for 20 minutes until reduced by about half, darkened slightly, and thickened. Keep warm for serving.
- Toast the Bottom Buns: Preheat oven to 350°F (180°C or Gas Mark 5). Slice the slider buns in half horizontally without separating the halves. Place the bottom buns, cut side up, on a parchment-lined baking sheet. Lightly brush with melted butter or aioli and toast for 5 minutes until golden.
- Assemble the Sliders: Spread a generous layer of garlic aioli on each toasted bottom bun. Pile on the thinly sliced roast beef about 2 to 3 layers deep. Place a slice of melty cheese on each slider, then sprinkle shredded mozzarella over the cheese. Spoon caramelized onions evenly over the sliders. Top with the bun halves.
- Prepare and Brush Garlic Butter Sauce: In a small bowl, mix melted butter with Worcestershire sauce, poppy seeds, sesame seeds, garlic powder, dried minced onion, kosher salt, and freshly cracked black pepper. Generously brush this mixture over the tops of the slider buns.
- Bake the Sliders: Cover the assembled sliders loosely with foil. Bake in the preheated oven for 10 minutes. Remove the foil and bake an additional 10 minutes until the tops are golden brown and the cheese is melted.
- Serve: Slice between the rolls to separate individual sliders. Serve warm with small bowls of the warm au jus sauce for dipping.
Notes
- For an easier 30-minute version, skip caramelizing onions and jazz up mayonnaise with the garlic aioli ingredients instead.
- Make sliders up to two days ahead without caramelized onions or garlic butter; add both just 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 avoid sogginess.
- Hawaiian slider buns are preferred for their sweetness and texture but any slider buns will work.
- Use good quality deli roast beef and melty cheeses like provolone or Swiss for best flavor.
- Slow caramelization of onions is key for deep flavor, so allow full cooking time.
Nutrition
- Serving Size: 1 slider
- Calories: 350 kcal
- Sugar: 3 g
- Sodium: 550 mg
- Fat: 22 g
- Saturated Fat: 9 g
- Unsaturated Fat: 11 g
- Trans Fat: 0.2 g
- Carbohydrates: 22 g
- Fiber: 1.5 g
- Protein: 15 g
- Cholesterol: 70 mg
