1. Prepare the Chicken

1. Preheat the Oven: Preheat your oven to 400°F (200°C) and grease a baking dish or line it with parchment paper.
2. Slice the Chicken: Place each chicken breast on a cutting board. Using a sharp knife, make horizontal cuts about ¾ of the way through the chicken, spacing the cuts about ½ inch apart. Be careful not to cut all the way through.
3. Season the Chicken: Rub the chicken with olive oil and season generously with paprika, garlic powder, onion powder, salt, and black pepper, ensuring the seasoning gets into the cuts.

2. Make the Spinach-Cheese Filling

1. Sauté the Spinach: Heat 1 tablespoon of olive oil or butter in a skillet over medium heat. Add the minced garlic and sauté for 30 seconds until fragrant. Stir in the spinach and cook for 2-3 minutes until wilted. If using frozen spinach, ensure it is fully thawed and drained before adding it to the skillet. Remove from heat and let cool slightly.
2. Mix the Filling: In a mixing bowl, combine the cooked spinach, cream cheese, shredded mozzarella, Parmesan, and red pepper flakes (if using). Mix until well combined.

3. Stuff the Chicken

1. Fill the Pockets: Spoon the spinach-cheese mixture into each cut of the chicken breast. Use about 1-2 teaspoons of filling per slit, ensuring the mixture is evenly distributed.
2. Arrange in the Baking Dish: Place the stuffed chicken breasts in the prepared baking dish.

4. Bake the Chicken

1. Bake: Bake the chicken in the preheated oven for 20-25 minutes, or until the chicken is cooked through and the internal temperature reaches 165°F (74°C).
2. Broil (Optional): For a golden-brown top, switch the oven to broil for the last 2-3 minutes of cooking.

5. Serve

1. Garnish: Sprinkle the chicken with fresh parsley and extra Parmesan cheese for added flavor and presentation.
2. Plate: Serve hot with your favorite side dishes, such as roasted vegetables, a fresh salad, or mashed potatoes.