01 - Preheat the oven to 400°F. Lightly grease a baking dish with cooking spray or a small amount of olive oil.
02 - In a medium bowl, combine crumbled feta cheese, chopped spinach, minced garlic, cream cheese, dill if using, salt, and black pepper. Mix thoroughly until all ingredients are well blended and a uniform filling forms.
03 - Using a sharp knife, carefully slice a horizontal pocket into the side of each chicken breast, stopping before cutting completely through. Open each pocket gently to create space for the filling.
04 - Generously fill each pocket with the spinach-feta mixture, pressing the filling in lightly. Secure the opening with toothpicks to prevent filling from escaping during cooking.
05 - Rub the outside of each stuffed chicken breast with olive oil. Season generously with additional salt and freshly ground black pepper on all sides.
06 - Place the stuffed chicken breasts in the prepared baking dish, arranging them in a single layer with space between each piece for even heat circulation.
07 - Bake for 25 to 30 minutes, or until the chicken is completely cooked through. The internal temperature should reach 165°F, and juices should run clear when pierced.
08 - Carefully remove and discard the toothpicks. Transfer the stuffed chicken breasts to serving plates and serve immediately with lemon wedges on the side for squeezing over the chicken.