French Onion Sliders Recipe

Close-up of a French onion slider with melted cheese and caramelized onions on a soft bun.

If you love French onion soup and cheeseburgers, these sliders are your perfect mash-up. They’re rich, flavorful, and easy enough for a casual weeknight dinner but impressive enough to serve guests. Make a batch for game day, holidays, or anytime you want something cozy and satisfying—no forks required.

Prep Time15

Cook Time30

Total Time45

Servings: sliders

Calories: 490kcal

Author: Sandra

Ingredients

For the Caramelized Onions:

2 tablespoons unsalted butter
2 tablespoons olive oil
2 large yellow onions thinly sliced
½ teaspoon kosher salt
½ teaspoon black pepper
1 teaspoon fresh thyme leaves or ½ teaspoon dried
1 teaspoon balsamic vinegar
½ cup beef broth (Note 1)

For the Beef Patties:

1 pound ground beef 80/20 blend recommended (Note 2)
1 teaspoon Worcestershire sauce
½ teaspoon kosher salt
½ teaspoon black pepper
½ teaspoon garlic powder
½ teaspoon onion powder
6 slider buns (Note 3)

For the Topping:

6 slices Gruyère cheese or Swiss (Note 4)
2 tablespoons mayonnaise optional (Note 5)
2 tablespoons Dijon mustard optional (Note 5)
2 tablespoons chopped fresh parsley for garnish

Instructions

In a large skillet, heat 2 tablespoons unsalted butter and 2 tablespoons olive oil over medium to medium-low heat.
Add sliced onions, ½ teaspoon kosher salt, and ½ teaspoon black pepper. Cook, stirring occasionally, until deeply golden and soft, about 25–30 minutes. Don’t rush. This step builds the flavor (Note 6).
2 large yellow onions
Stir in 1 teaspoon fresh thyme leaves and 1 teaspoon balsamic vinegar. Cook 1 more minute.
Add ½ cup beef broth and simmer for 5 minutes, until the liquid reduces and lightly coats the onions. Remove from heat (Note 1).
In a bowl, gently combine 1 pound ground beef, 1 teaspoon Worcestershire sauce, ½ teaspoon kosher salt, ½ teaspoon black pepper, ½ teaspoon garlic powder, and ½ teaspoon onion powder.
Divide into 6 equal portions and form into 2½–3 inch patties, just slightly wider than your buns (Note 7).
Heat a skillet or grill over medium-high. Cook patties for 3–4 minutes per side or to desired doneness.
In the last minute, top each with a slice of Gruyère and cover the pan to melt the cheese (Note 8).
6 slices Gruyère cheese
If desired, lightly toast slider buns for added flavor and structure (Note 3).
Spread mayonnaise and Dijon mustard on the bottom buns, if using (Note 5).
Add the cheesy patties, top with caramelized onions, and sprinkle with parsley.
Add top buns and serve warm.

Notes

Use low-sodium beef broth to avoid over-salting. The broth should reduce and lightly coat the onions without being watery.
An 80/20 beef blend balances flavor and moisture. Avoid overmixing to keep the patties tender.
Soft slider buns like brioche or potato rolls work best. Toasting helps prevent sogginess and adds a subtle crunch.
Gruyère melts beautifully and brings a classic French onion soup flavor. Swiss is a good budget-friendly alternative.
Mayo and mustard are optional but add creamy contrast and tang to the savory filling.
Caramelizing onions takes time. Keep heat moderate and stir occasionally. Onions should be deep golden and jammy by the end.
Shaping patties slightly larger than the buns accounts for shrinkage during cooking.
To melt cheese evenly, cover the pan with a lid, a sheet of foil, or an inverted baking sheet.
The onions can be made up to 3 days ahead and stored in an airtight container in the fridge. Reheat gently before serving.
Freezer Tip: Cooked patties freeze well for up to 2 months. Reheat in a skillet or oven.

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