Preheat the oven to 375°F (190°C).

In a bowl, mix together chopped spinach, cream cheese, mozzarella cheese, garlic, oregano, salt, and black pepper until well combined.

Slice each chicken breast horizontally to create a pocket.

Stuff each chicken breast with the spinach mixture and secure with toothpicks if necessary.

Heat olive oil in a skillet over medium heat. Sear the stuffed chicken breasts on both sides until golden brown, about 3-4 minutes per side.

Transfer seared chicken to a baking dish and sprinkle with parmesan cheese.

Bake in the preheated oven for 25-30 minutes, or until the chicken is cooked through and no longer pink in the center.