From https://tasty.co/recipe/cheesy-french-onion-chicken

Ingredients

• 6 boneless, skinless chicken thighs
• salt, to taste
• pepper, to taste
• 1 tablespoon garlic, minced
• 1 tablespoon dried parsley
• 1 tablespoon butter
• 6 large onions, thinly sliced
• 1 tablespoon fresh thyme
• 1 cup beef stock (235 mL)
• 2 cups gruyere cheese (200 g), shredded
• bread (french stick), sliced and toasted, to serve

Method

1. In a bowl, add the chicken thighs, salt, pepper, garlic, dried parsley, and olive oil, and toss until evenly coated.
2. Add the chicken to a skillet on medium-high heat. Sear until golden brown, about 4 minutes. Flip and cook the other side of the chicken, 2 minutes. Remove the chicken from the pan and set aside.
3. Preheat oven to grill
4. Add the butter, sliced onions, salt, and pepper to the same pan, stirring occasionally until softened. Reduce heat to low and cook until they are deeply caramelised, about 1 hour.
5. Add thyme and beef stock and bring the mixture to a simmer.
6. Add the chicken on top of the onions, and sprinkle with Gruyère cheese.
7. Grill for 5 minutes, until the cheese is melted and golden brown.
8. Serve over bread