Description

These Buttery Roast Beef Sliders with Caramelized Onions are an irresistible snack or appetizer featuring tender deli roast beef, melty cheese, and sweet caramelized onions on toasted Hawaiian slider buns. Topped with a flavorful garlic butter sauce and served with rich au jus for dipping, these sliders are perfect for game day, parties, or a cozy meal. The homemade garlic aioli adds a creamy touch, making these sliders wonderfully savory and satisfying.

Ingredients

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For the 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

For the 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

For the Au Jus Sauce

¼ cup unsalted butter
1 tablespoon Better than Bouillon Beef Base
2 cups beef broth
2 teaspoons Worcestershire sauce

For the 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

For the 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

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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 kosher salt and set aside. Alternatively, for a quicker version, mix mayo with garlic, mustard, lemon, and salt.
Prepare the Au Jus Sauce: 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, thickens slightly, and darkens in color. Keep warm for serving.
Toast the Bottom Buns: Preheat your oven to 350°F (180℃). Slice the buns in half horizontally without separating them. Place the bottom buns cut-side up on a parchment-lined baking sheet. Lightly brush them with melted butter or aioli and toast in the oven for 5 minutes until lightly golden.
Assemble the Sliders: Spread a generous layer of garlic aioli over the toasted bottom buns. Pile the roast beef evenly over the buns, layering 2–3 slices per slider. Lay down your choice of melty cheese slices, then sprinkle shredded mozzarella for extra meltiness. Spoon caramelized onions evenly over the top.
Add the Tops and Garlic Butter: Place the top halves of the slider buns over the assembled ingredients. 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 garlic butter sauce over the tops of the buns.
Bake the Sliders: Cover the sliders loosely with foil and bake in the preheated oven for 10 minutes. Remove the foil and bake for an additional 10 minutes until the tops are golden brown and cheeses are melted and bubbly.
Serve: Slice between the rolls to separate the sliders. Serve warm with bowls of the hot au jus sauce on the side for dipping. Enjoy immediately.

Notes

For a quicker 30-minute version, skip the caramelized onions and jazz up mayonnaise with garlic aioli ingredients before assembling.
You can assemble sliders up to two days ahead without onions or garlic butter; add those just before baking.
Store leftover sliders in an airtight container for up to 3 days.
Reheat leftovers in the oven at 375°F for about 10 minutes to avoid sogginess.
Substitute your favorite melty cheeses like muenster, provolone, or Swiss for varied flavor.
If you prefer not to use raw egg yolk, mayonnaise is a safe and tasty alternative for aioli.

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: 14 g
Cholesterol: 75 mg