Preheat your oven to 375°F (190°C).
In a bowl, mix the cream cheese, spinach, sun-dried tomatoes, mozzarella, garlic, salt, and pepper.
Carefully slice the chicken breasts horizontally to create a pocket.
Stuff each chicken breast with the filling mixture.
Secure the openings with toothpicks or kitchen twine.
Heat olive oil in an oven-safe skillet over medium heat.
Sear the stuffed chicken breasts for 4-5 minutes on each side until golden brown.
Transfer the skillet to the preheated oven.
Bake for 20-25 minutes or until the chicken is cooked through.
Let rest for 5 minutes before serving.