Step by step

Method

4 steps

1. 1

   Pat 4 boneless chicken breasts dry and season both sides with salt and pepper. If they're thick, pound to even thickness so they cook at the same pace. Heat 1 tablespoon olive oil in a large skillet over medium-high and sear 3–4 minutes per side until deep golden; move to a plate (they'll finish later).

2. 2

   Drop heat to medium. Add 2 tablespoons butter and 2 large thinly sliced onions. Cook 15–20 minutes, stirring every few minutes, until the onions are deeply golden and jammy — pale onions mean you rushed it. Add 2 minced garlic cloves and 1 teaspoon fresh thyme (or ½ teaspoon dried) for 1 minute until fragrant.

3. 3

   Pour in 1 cup beef broth and 1 tablespoon Worcestershire, scraping up the browned bits. Nestle the chicken back in with any juices. Cover and simmer 10–12 minutes until the thickest part hits 165°F.

4. 4

   Scatter 1 cup shredded Gruyère or Swiss over the chicken, cover 1–2 minutes until melted and stretchy. Serve with toasted baguette slices if you want that classic French-onion dunk. You want juicy chicken under sweet caramelized onions and gooey cheese — not pale undercooked onions or dry overcooked breast.