Ingredients
- 4 boneless, skinless chicken breasts, pounded even
- 1 tsp kosher salt, divided
- 1/2 tsp black pepper
- 3 large yellow onions, thinly sliced
- 3 tbsp unsalted butter
- 1 tbsp olive oil
- 1 tsp sugar
- 1/2 cup beef broth
- 1 tbsp balsamic vinegar
- 1 tsp fresh thyme leaves, plus more for serving
- 1 1/2 cups shredded Gruyère cheese
- Crusty bread, for serving
Instructions
- Caramelize the onions. Melt the butter with the olive oil in a large oven-safe skillet over medium heat. Add the onions, 1/2 teaspoon salt, and the sugar; cook 18–20 minutes, stirring occasionally, until deeply golden and jammy.
- Season the chicken. While the onions cook, season the chicken with the remaining 1/2 teaspoon salt and the pepper.
- Deglaze. Stir the beef broth, balsamic vinegar, and thyme into the onions, scraping up the browned bits. Simmer 2 minutes until slightly reduced. Transfer the onions to a plate.
- Sear the chicken. In the same skillet over medium-high heat, sear the chicken 5–6 minutes per side until golden and cooked through (165°F).
- Smother and broil. Spoon the caramelized onions generously over each breast and top with Gruyère. Broil 2–3 minutes until the cheese is melted, bubbling, and spotty-brown.
- Serve. Shower with fresh thyme and serve with crusty bread for scooping up every last onion.
💡 French onion smarts
Patience with the onions pays off — true caramelization takes a full 18–20 minutes; rushing gives you merely soft onions. Gruyère is the classic for its nutty melt, but Swiss or provolone work in a pinch. Pounding the chicken even ensures it cooks through without drying. Deglazing with the broth captures every caramelized bit from the pan — that fond is pure flavor.
Common questions
Can I use chicken thighs?
Yes — boneless thighs stay extra juicy. Sear 5–6 minutes per side and check for 165°F inside.
Can I make it ahead?
Caramelize the onions up to 3 days ahead and refrigerate. Sear the chicken fresh, then assemble and broil — dinner in 15 minutes.
What if I don't have Gruyère?
Swiss is the closest swap; provolone or mozzarella melt well too, though you lose Gruyère's signature nuttiness.
Is this gluten-free?
Yes, as written — just serve with gluten-free bread or over mashed potatoes instead of crusty bread.
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