Prepare the Filling

1. Sauté the Mushrooms: In a skillet over medium heat, melt 2 tablespoons of butter. Add the chopped mushrooms and sauté for 5-7 minutes until they are softened and any liquid has evaporated. Stir in the minced garlic and cook for an additional 1 minute.

2. Mix the Filling: In a bowl, combine the sautéed mushrooms and garlic with cream cheese, shredded mozzarella, Parmesan cheese, dried thyme, salt, and pepper. Mix until well combined.

Stuff the Chicken

1. Prepare the Chicken: Preheat your oven to 375°F (190°C). Carefully slice a pocket into each chicken breast, being careful not to cut all the way through.

2. Stuff the Chicken: Generously fill each chicken breast pocket with the cheesy mushroom mixture. Use toothpicks to secure the openings if necessary.

Bake the Chicken

1. Arrange in Baking Dish: Place the stuffed chicken breasts in a greased baking dish.

2. Bake: Bake in the preheated oven for 25-30 minutes or until the chicken is cooked through and reaches an internal temperature of 165°F (74°C).

3. Broil for Color (Optional): For a golden-brown top, switch the oven to broil for the last 3-5 minutes of cooking, keeping a close eye to prevent burning.

Serve

1. Garnish: Remove the toothpicks and transfer the stuffed chicken to a serving platter. Garnish with chopped fresh parsley.

2. Enjoy: Serve warm with your choice of sides, such as roasted vegetables or a fresh salad.