Step 1: Caramelize the Onions

1. In a large skillet, heat 2 tablespoons of olive oil over medium heat.
2. Add the thinly sliced onions and sprinkle with a pinch of salt. Sauté for about 15-20 minutes, stirring occasionally, until the onions are golden brown and caramelized. Be patient; this step is crucial for developing flavor!

You want the onions to be deeply caramelized, so don’t rush this process. The longer you cook them, the sweeter and more flavorful they become.

Step 2: Prepare the Chicken

1. While the onions are caramelizing, season the chicken breasts with salt, pepper, and thyme on both sides.
2. In another skillet, heat a bit more oil over medium-high heat. Add the seasoned chicken breasts and cook for about 5-7 minutes on each side, or until they’re golden brown. They don’t need to be cooked through yet, as they’ll finish cooking in the oven.

This step not only seals in moisture but also creates a lovely crust that adds flavor to the dish.

Step 3: Combine and Bake

1. Preheat your oven to 375°F (190°C).
2. Once the onions are caramelized, remove them from the heat and set aside.
3. In a baking dish, pour in the beef broth to create a flavorful base. Place the browned chicken breasts on top of the broth.
4. Spoon the caramelized onions evenly over the chicken, and then sprinkle the shredded Gruyère cheese on top.

Step 4: Bake

1. Cover the baking dish with aluminum foil and bake in the preheated oven for about 15-20 minutes.
2. Remove the foil and bake for an additional 10 minutes, or until the cheese is bubbly and golden, and the chicken reaches an internal temperature of 165°F (74°C).