01 - Preheat your oven to 400°F. Lightly coat a suitable baking dish with cooking spray or butter to prevent sticking.
02 - In a medium mixing bowl, combine the chopped fresh spinach, drained and chopped artichoke hearts, softened cream cheese, shredded mozzarella, grated Parmesan, minced garlic, and optional crushed red pepper flakes. Stir until the mixture is thoroughly combined and uniform.
03 - Place each chicken breast on a clean cutting board. Using a sharp utility knife, carefully create a deep pocket in the thickest side of each breast, ensuring you do not slice completely through to the other side.
04 - Evenly distribute the spinach-artichoke filling into the prepared pocket of each chicken breast. If necessary, use one or two toothpicks to secure the opening and keep the filling contained during baking.
05 - Brush the exterior of each stuffed chicken breast with olive oil. Season generously on all sides with salt, black pepper, and paprika.
06 - Arrange the seasoned, stuffed chicken breasts in the prepared baking dish. Bake for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) and the juices run clear when pierced.
07 - Carefully remove any toothpicks before serving. Allow the chicken to rest for 5 minutes outside the oven before slicing and serving. Garnish with freshly chopped parsley, if desired.