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 mixing bowl, combine the crumbled feta cheese, chopped spinach, minced garlic, cream cheese, fresh dill, salt, and black pepper. Mix thoroughly until all ingredients are evenly distributed and the mixture forms a cohesive filling.
03 - Using a sharp knife, carefully slice a horizontal pocket into the side of each chicken breast, ensuring you do not cut completely through to the other side. Leave about 1/2 inch uncut to hold the filling securely.
04 - Generously fill each chicken breast pocket with the spinach and feta mixture. If the pockets are loose, secure with toothpicks by inserting them at an angle through the opening to prevent the filling from escaping during cooking.
05 - Rub the outside of each stuffed chicken breast with olive oil, then season generously with additional salt and black pepper to ensure the exterior is well-seasoned.
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. To test doneness, insert a thermometer into the thickest part of the breast—it should register 165°F, or the juices should run clear when pierced.
08 - Carefully remove any toothpicks from the chicken breasts. Serve immediately with fresh lemon wedges on the side for squeezing over the chicken.