Preheat the oven: Set your oven to 375°F (190°C). Line a baking sheet with parchment paper or lightly grease it to prevent sticking.
Prepare the chicken: Using a sharp knife, cut a pocket into each chicken breast — be careful not to slice all the way through. In a bowl, combine the chopped mushrooms, softened cream cheese, mozzarella cheese, minced garlic, thyme, parsley, salt, and pepper. Mix until evenly combined, forming a creamy filling. Spoon the mixture into each chicken pocket, pressing gently to secure the filling.
Sear the chicken: In a large skillet, melt the butter over medium heat. Once hot and bubbly, add the stuffed chicken breasts. Sear for 3–4 minutes on each side until golden brown. The goal is to develop a flavorful crust without fully cooking the chicken.
Bake to perfection: Transfer the seared chicken breasts to the prepared baking sheet. Sprinkle the tops with grated Parmesan cheese. Bake in the preheated oven for 20–25 minutes, or until the internal temperature reaches 165°F (74°C) and the cheese is melted and lightly browned on top.
Garnish and serve: Remove from the oven and let the chicken rest for 5 minutes before serving to lock in the juices. Garnish with fresh parsley for a bright finishing touch. Serve hot with roasted vegetables, mashed potatoes, or a light salad for a complete meal.
