Preheat your oven to 375°F (190°C).
In a mixing bowl, combine cream cheese, mozzarella, spinach, minced garlic, and a pinch of salt and pepper. Mix until smooth.
Using a sharp knife, carefully cut a pocket into each chicken breast without slicing all the way through.
Season the chicken on both sides with salt, pepper, and Italian seasoning.
Spoon the spinach and cheese mixture into each pocket. Secure the edges with toothpicks or kitchen twine.
Heat olive oil in a skillet over medium-high heat. Sear the chicken for 2–3 minutes on each side until golden brown.
Transfer the chicken to a baking dish and bake for 20–25 minutes, or until the internal temperature reaches 165°F.
Let the chicken rest for a few minutes before serving. Remove toothpicks or twine.