Preheat the oven to 375°F (190°C).

Slice a pocket into each chicken breast by making a horizontal cut about 3/4 of the way through the breast.

In a skillet, heat the olive oil over medium heat. Add the garlic and sauté until fragrant.

Add the mushrooms to the skillet and cook until they have softened and released their moisture. Remove from heat.

Stuff each chicken breast with a handful of fresh spinach, sautéed mushrooms, and a sprinkle of shredded mozzarella cheese. Use toothpicks to secure if needed.

Season the stuffed chicken breasts with salt and pepper.

Heat a separate oven-safe skillet over medium-high heat. Add the stuffed chicken breasts and sear on each side for about 2-3 minutes, until browned.

Transfer the skillet to the preheated oven and bake for about 20-25 minutes or until the chicken is cooked through.

Remove the toothpicks before serving. Pair with your favorite side dish or a fresh salad. Enjoy!