Let’s walk through the steps to create this delicious dish:

1. Preheat your oven to 375°F (190°C). Prepare a baking dish by lightly greasing it with olive oil.
2. In a skillet over medium heat, warm the olive oil. Add the chopped mushrooms and garlic, sautéing until the mushrooms are tender and the garlic is fragrant, about 5 minutes.
3. Remove the skillet from the heat and stir in the mozzarella, Parmesan, and chopped parsley. Season with salt and pepper to taste.
4. Using a sharp knife, carefully cut a pocket into each chicken breast. Fill each pocket with the mushroom and cheese mixture, securing with toothpicks if necessary.
5. Season the outside of the chicken breasts with salt, pepper, and Italian seasoning.
6. In the same skillet, melt the butter over medium-high heat. Add the stuffed chicken breasts and sear each side until golden brown, about 4 minutes per side.
7. Transfer the chicken to the prepared baking dish. Bake in the preheated oven for 20-25 minutes, or until the chicken is cooked through and the cheese is bubbling.
8. Let the chicken rest for 5 minutes before serving, allowing the juices to redistribute.

Cooking always reminds me of the patience my grandmother had as she lovingly prepared meals, and this dish is no exception. Taking the time to sear the chicken ensures a beautiful crust, a tip I learned from watching her in action.