Ingredients:
- 6 boneless, skinless chicken thighs (about 900g / 2 lbs)
- 1 tablespoon olive oil (15 ml)
- 1 teaspoon kosher salt (5g)
- ½ teaspoon black pepper (2.5g)
- 3 large yellow onions, thinly sliced (about 900g / 2 lbs)
- 2 tablespoons unsalted butter (28g)
- 1 tablespoon olive oil (15 ml)
- 1 teaspoon brown sugar (5g)
- ½ teaspoon dried thyme (2.5g)
- 1/4 teaspoon salt (1.25g)
- 1/4 teaspoon black pepper (1.25g)
- 2 cloves garlic, minced
- 2 tablespoons all-purpose flour (16g)
- 1 cup dry white wine (e.g., Sauvignon Blanc or Pinot Grigio) (240 ml)
- 2 cups low-sodium chicken broth (480 ml)
- 1 tablespoon Worcestershire sauce (15 ml)
- 1 French baguette, sliced into ½-inch rounds (about 12 slices)
- 2 cups shredded Gruyere cheese (about 225g / 8 oz)
Instructions:
- Season chicken thighs with salt and pepper.
- Heat olive oil in an oven-safe skillet over medium-high heat. Sear chicken thighs on both sides until golden brown. Remove chicken from skillet and set aside.
- Add butter and olive oil to the skillet. Add sliced onions, brown sugar, thyme, salt, and pepper. Cook over medium-low heat, stirring occasionally, until onions are deeply caramelized and golden brown (about 30-40 minutes).
- Stir in minced garlic and cook for 1 minute until fragrant. Sprinkle flour over the onions and cook for 1 minute more.
- Gradually pour in white wine, scraping up any browned bits from the bottom of the skillet. Let the wine reduce slightly.
- Pour in chicken broth and Worcestershire sauce. Bring to a simmer.
- Return chicken thighs to the skillet, nestling them among the onions.
- Arrange baguette slices on top of the chicken and onions. Sprinkle generously with shredded Gruyere cheese.
- Bake in a preheated oven at 375°F (190°C) for 20-25 minutes, or until the cheese is melted, bubbly, and golden brown, and the internal temperature of the chicken reaches 165°F (74°C).
- Let the casserole rest for 5-10 minutes before serving. This allows the sauce to thicken slightly.