Prepare the Mushroom Filling

1. Sauté the Mushrooms: Heat 2 tablespoons of butter in a skillet over medium heat. Add the chopped mushrooms and cook for 5–7 minutes until softened and golden. Stir in minced garlic and dried parsley, cooking for another 1–2 minutes until fragrant.
2. Cool and Combine: Remove the mushroom mixture from the heat and allow it to cool slightly. Mix in the shredded mozzarella and grated Parmesan cheeses. Set aside.

Prepare the Chicken

3. Butterfly the Chicken Breasts: Place each chicken breast on a cutting board. Using a sharp knife, cut a pocket into the side of each breast, being careful not to cut all the way through.
4. Season the Chicken: Rub the chicken breasts with olive oil and season generously with smoked paprika, garlic powder, onion powder, dried thyme, salt, and black pepper.

Stuff the Chicken

5. Add the Filling: Spoon the prepared mushroom mixture into each chicken pocket, filling generously but not overstuffing. Secure the edges with toothpicks to keep the filling in place during cooking.

Cook the Chicken

6. Sear the Chicken: Heat 2 tablespoons of olive oil in a large skillet over medium-high heat. Sear the stuffed chicken breasts for 3–4 minutes per side, until golden brown.
7. Bake to Finish: Transfer the skillet to a preheated oven at 375°F (190°C) and bake for 12–15 minutes, or until the internal temperature of the chicken reaches 165°F (74°C).

Make the Garlic Butter Sauce

8. Prepare the Sauce: In a small saucepan, melt 3 tablespoons of butter over medium heat. Add minced garlic and cook until fragrant, about 1 minute. Stir in chicken broth or white wine, dried parsley, and lemon juice. Simmer for 2–3 minutes.

Serve

9. Plate the Chicken: Remove the toothpicks from the chicken and place on a serving platter. Drizzle the garlic butter sauce over the chicken and garnish with fresh parsley if desired.