In a bowl, crumble the feta cheese and grate or finely chop the mozzarella. Add the chopped parsley and beat in 3 eggs until combined. Set aside. Prepare the chicken fillets: Season the chicken fillets on both sides with salt, black pepper, and sweet paprika. Using a sharp knife, carefully slice each fillet horizontally to create a pocket without cutting all the way through. Stuff the fillets: Spoon the cheese and egg mixture evenly into each chicken pocket. Press gently to seal the filling inside. Wrap the fillets: Place each stuffed fillet on parchment paper and wrap it securely. Then wrap again in aluminum foil to hold the shape and prevent leakage. Cook the chicken: Heat oil in a frying pan over medium heat. Place the wrapped fillets in the pan and fry gently for about 7-8 minutes on each side until golden brown and cooked through. Alternatively, you can bake wrapped fillets in a preheated oven at 180°C (350°F) for 25-30 minutes. Serve: Carefully unwrap the chicken fillets and slice if desired. Serve hot with your favorite side dishes like roasted vegetables, rice, or salad. Serving and Storage Tips