01 - Preheat the oven to 400°F. Lightly grease a baking dish with cooking spray or a small amount of oil.
02 - In a mixing bowl, combine crumbled feta cheese, chopped spinach, minced garlic, cream cheese, fresh dill, salt, and black pepper. Mix until thoroughly blended and creamy.
03 - Using a sharp knife, slice a horizontal pocket into each chicken breast, cutting carefully from the thicker side without cutting completely through. Open pockets gently with fingers.
04 - Divide the spinach-feta mixture evenly among chicken breasts. Stuff each pocket generously, pressing filling to distribute. Secure openings with toothpicks if needed to prevent filling from escaping.
05 - Rub the outside of each stuffed breast with olive oil. Season generously with additional salt and pepper on all sides.
06 - Place stuffed chicken breasts in the prepared baking dish, leaving slight space between pieces for even heat circulation.
07 - Bake for 25-30 minutes, or until chicken is completely cooked through and juices run clear when pierced. Internal temperature should reach 165°F at the thickest part.
08 - Remove from oven and carefully remove toothpicks. Let rest for 3-5 minutes before serving. Accompany with fresh lemon wedges for squeezing over the chicken.