Preheat your oven to 375°F (190°C).

In a medium bowl, combine the chopped spinach, cream cheese, mozzarella cheese, garlic powder, onion powder, salt, and pepper. Mix until well combined.

Using a sharp knife, create a pocket in each chicken breast by slicing horizontally, being careful not to cut all the way through.

Stuff each chicken breast with the spinach and cheese mixture, securing the opening with toothpicks if necessary.

Heat the olive oil in an oven-safe skillet over medium-high heat. Once hot, add the stuffed chicken breasts and sear for about 3-4 minutes on each side until golden brown.

Sprinkle the grated Parmesan cheese on top of the chicken breasts.

Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (75°C).

Remove from the oven and let rest for 5 minutes before serving.