01 - Preheat oven to 400°F (200°C). Lightly grease a baking dish.
02 - In a medium bowl, mix spinach, artichoke hearts, cream cheese, mozzarella, Parmesan, garlic, and red pepper flakes until well combined.
03 - Place chicken breasts on a cutting board. Using a sharp knife, carefully cut a pocket into the side of each breast, being careful not to cut all the way through.
04 - Stuff each chicken breast evenly with the spinach-artichoke mixture. Secure with toothpicks if needed.
05 - Rub chicken breasts with olive oil, then season with salt, black pepper, and paprika.
06 - Arrange stuffed breasts in the prepared baking dish. Bake for 25–30 minutes, or until the chicken is cooked through (internal temperature of 165°F) and juices run clear.
07 - Remove toothpicks. Let rest for 5 minutes before serving. Garnish with fresh parsley if desired.