Ingredients
Method
- Season chicken breasts with salt, pepper, and garlic powder. Heat olive oil and 1 tbsp butter in a 12-inch oven-safe skillet over medium-high heat. Sear chicken for 5-6 minutes per side until golden. Transfer to a plate.
- Reduce heat to medium. Melt remaining 2 tbsp butter in skillet. Add sliced onions and a pinch of salt. Cook for 18-20 minutes, stirring often, until deep golden-amber. Stir in garlic and thyme; cook for 1 minute.
- Sprinkle flour over onions and stir for 1 minute. Pour in beef broth, balsamic vinegar, and Worcestershire sauce. Simmer for 3-4 minutes until thick and glossy.
- Return chicken and resting juices to skillet, spooning jammy onions over each breast. Top with shredded Gruyère and mozzarella cheese.
- Place skillet under the oven broiler on HIGH for 3-4 minutes until cheese is bubbly and golden-blistered. Garnish with fresh thyme and serve hot with crusty bread.