Preparation Steps

• Preheat oven to 375°F (190°C). In a large skillet over medium heat, melt 1 tablespoon butter. Add sliced onions, sugar, salt, and pepper. Cook, stirring occasionally, for 20–25 minutes until deeply caramelized and golden brown.
• Add minced garlic and cook for 1 minute more. Remove from heat and set aside.
• In the same skillet, heat olive oil over medium-high heat. Season chicken pieces with salt and pepper. Cook until lightly browned and cooked through, about 5–6 minutes. If using, add white wine and simmer for 2 minutes to deglaze the pan.
• Stir in chicken broth, heavy cream, Worcestershire sauce, and thyme. Bring to a gentle simmer and cook for 5 minutes. Remove from heat and stir in caramelized onions.
• Transfer mixture to a greased 9x13-inch baking dish. Sprinkle Gruyère and Parmesan cheeses evenly over the top.
• Roll out puff pastry to fit the dish, place it on top, and trim any excess. Cut a few small slits in the center to allow steam to escape. Bake for 25–30 minutes, or until pastry is puffed and golden brown.