In a mixing bowl, combine the softened cream cheese, chopped fresh spinach, chopped artichoke hearts, grated Parmesan, shredded mozzarella, and minced garlic. Season with salt and pepper. Stir until well combined and creamy.
Lay each chicken breast flat on a cutting board. Carefully slice a pocket into the side of each breast, not cutting all the way through. Season inside and outside with salt and pepper.
Spoon the spinach and artichoke cream cheese mixture into each pocket evenly. Use toothpicks if needed to secure the filling inside.
Heat olive oil in a skillet over medium-high heat. Sear the stuffed chicken breasts for about 3-4 minutes on each side until golden brown.
Transfer the skillet to a preheated oven at 375°F (190°C). If skillet isn’t oven-safe, move chicken to a baking dish. Bake for 20-25 minutes until chicken reaches 165°F (74°C) internal temperature.
Remove toothpicks, let chicken rest for a few minutes, then serve with your choice of sides.