French Onion Burgers

published Jun 7, 2023
French Onion Burger Recipe

These grilled hamburgers are piled high with caramelized onions and melty Gruyère cheese.

ServesServes 4

Prep15 minutes

Cook30 minutes to 1 hour 10 minutes

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Credit: Kelli Foster

The burger I’ll be grilling all summer long takes its inspiration from the classic French onion soup, one of my family’s favorite winter dinners. These juicy, grilled burgers are piled high with caramelized onions, topped with melty Gruyère cheese, and served on buttery, toasted brioche buns. 

What Is the Difference Between Grilled Onions and Caramelized Onions?

Grilled onions and caramelized onions are two completely different things. The former are cooked quickly directly on grill grates, while the latter are cooked slowly in a heavy-bottomed pan until they’re sweet and jammy. 

How to Set Up Your Grill for French Onion Burgers

The onions and the burger patties start over direct heat, then move to indirect heat to finish cooking. If you’re cooking on a gas grill, leave at least one burner unlit, so that foods can be grilled adjacent to and directly above the heat source. For a charcoal grill, open the bottom vents and place 1/2 chimney of unlit charcoal on one side of the coal grate. Light a full chimney of charcoal, then when ready, pour the ashy coals directly on top of the unlit coals. The extra coals are insurance against the charcoal burning out while you caramelize the onions.

Credit: Kelli Foster

Tips for Caramelizing Onions on the Grill

  • Add unlit coals to extend burn time. The burgers cook in under 10 minutes, but it takes a bit longer to caramelize the onions. Keep the heat steady for longer by piling lit charcoal over a few handfuls of unlit charcoal. The ashy pieces will slowly light the charcoal, extending the burn time.
  • Use a cast iron skillet. Cast iron skillets are made to withstand the intense heat of gas and charcoal grills. These skillets have a thick bottom that distributes heat evenly. 
  • Take your time. It takes time to coax the moisture from the slices of onion and intensify the natural sugars. Start the onions over direct heat, but if they start to burn or cook too quickly, move to indirect heat to finish. It should take 20 to 30 minutes. 
  • Freeze extra onions. Freeze any extra caramelized onions in ice cube trays or mini muffin tins. You can thaw the onions to use on future burgers or to add to dips and galettes

French Onion Burger Recipe

These grilled hamburgers are piled high with caramelized onions and melty Gruyère cheese.

Prep time 15 minutes

Cook time 30 minutes to 1 hour 10 minutes

Serves Serves 4

Nutritional Info

Ingredients

  • 4 tablespoons

    (1/2 stick) unsalted butter, divided

  • 1 1/2 pounds

    yellow onions (about 3 medium)

  • 8 sprigs

    fresh thyme, divided

  • 2 1/4 teaspoons

    kosher salt, divided, plus more as needed

  • 2 teaspoons

    onion powder

  • 1/2 teaspoon

    garlic powder

  • 3/4 teaspoon

    freshly ground black pepper, divided, plus more for serving

  • 1 1/4 pounds

    ground beef (80% lean / 20% fat)

  • 1/4 cup

    dry white wine

  • 1 teaspoon

    balsamic or sherry vinegar

  • 2 ounces

    sliced Gruyère cheese

  • 4

    split hamburger buns, preferably brioche

  • Baby arugula (optional)

Instructions

  1. Let 4 tablespoons unsalted butter sit at room temperature until softened. Meanwhile, heat the grill, make the patties, and cook the onions.

  2. Heat an outdoor gas grill for medium, indirect heat (about 350°F) or until you can hold your hand an inch over the grates for 3 to 4 seconds. For a gas grill, light 2 burners to medium and leave one burner off. For a charcoal grill, arrange 1/2 chimney of unlit lump charcoal on one half of the lower grate. Then light 1 chimney full of lump charcoal. When the coals are white and ashy, pour onto the unlit charcoal, arranging the coals to create a high heat and a low heat cooking zone (direct and indirect grilling).

  3. Halve and thinly slice 1 1/2 pounds yellow onions (about 4 cups). Pick the leaves from 8 fresh thyme sprigs until you have 1 tablespoon.

  4. Place 1 1/2 teaspoons of the kosher salt, 2 teaspoons onion powder, 1/2 teaspoon garlic powder, and 1/4 teaspoon black pepper in a large bowl and stir to combine. Add 1 1/4 pounds ground beef and mix with your fingertips until the seasoning is evenly distributed. Do not overmix. Divide into 4 (5-ounce) portions. Use your hands to gently flatten each portion into a patty about 3/4-inch thick and press your thumb into the center to create a shallow divot. Let the burgers sit at room temperature until the onions are finished cooking, about 30 minutes.

  5. When the grill is ready, place 2 tablespoons of the butter in a 12-inch cast iron or other grill-safe, heavy bottomed skillet. Place over medium, direct heat until melted. Add the onions, thyme, remaining 3/4 teaspoon kosher salt, and remaining 1/2 teaspoon black pepper. Cook, stirring frequently with a wooden spoon, until the onions have reduced by half, are very soft, and deep golden-brown, 20 to 25 minutes on a charcoal grill and 50 to 55 minutes on a gas grill. Cover between stirs if using a gas grill, or cook uncovered if using a charcoal grill. Move the pan temporarily to indirect heat (over an unlit burner or away from the pile of coals) if the onions start to burn.

  6. Position the skillet over direct heat. Pour 1/4 cup dry white wine over the caramelized onions and scrape up any browned bits on the bottom of the pan. Continue to stir until the wine is evaporated, about 20 seconds. Remove the pan from the heat, add 1 teaspoon balsamic or sherry vinegar, and stir to combine.

  7. Place the patties on the grill in a single layer over direct heat. Cook uncovered until grill marks form on the bottom and the burgers release easily from the grill grates, 2 to 4 minutes. Flip and cook until grill marks appear on the second side, about 2 minutes more. Move the patties to indirect heat and continue to grill 3 to 5 minutes more for medium-rare burgers (120 to 125°F), 6 to 8 minutes more for medium (130 to 135°F), or 8 to 10 minutes more for medium-well burgers (140 to 145°F).

  8. In the last 2 to 3 minutes of cooking, place 2 ounces Gruyère cheese on top of the patties. Spread the remaining 2 tablespoons butter over the cut sides of 4 hamburger buns. Arrange buns, buttered-side down over direct heat and grill until lightly toasted, turning once, about 10 seconds.

  9. Place a small handful of baby arugula, if using, on each bottom bun. Top each bottom bun with 1 burger patty. Divide the caramelized onions evenly among the burgers and grind some more black pepper on top. Close with the top buns.

Recipe Notes

Make ahead: The burger patties can be prepared, formed, and refrigerated up to 1 day in advance. Remove from the refrigerator before caramelizing the onions and let sit at room temperature. The caramelized onions can be made up to 1 week in advance on the grill or on stovetop and refrigerated until ready to use.

Stovetop variation: Caramelize onions on the stovetop over medium-low heat according to the instructions above. Reduce the heat to low if the onions begin to burn. Once the onions are done cooking, remove them from the skillet and wipe clean with a damp paper towel. Add 1 additional tablespoon unsalted butter to the skillet and cook the burger patties over medium heat according to the instructions above, reducing the heat to low once the burger patties have browned on both sides and cooking until desired doneness.

Storage: Refrigerate cooked burger patties in an airtight container for up to 2 days. Refrigerate caramelized onions in an airtight container for up to 1 week or freeze for up to 3 months.