In a large Ziploc bag combine the juice of 1 lemon, 4 tablespoons of olive oil, garlic, and red pepper flakes. Mince 6 fresh sage leaves and add to the bag. Shake well to combine.
Butterfly the chicken breasts and add them to the bag. Shake well to coat and marinate for 1 – 4 hours (longer is better).
Remove chicken from the bag and lay 3 slices of prosciutto inside the chicken breast. Fold over the other side and secure with toothpicks or skewers.
Grill until chicken is done (approximately 5 minutes per side). Remove from the grill and let rest for 5 minutes.
Meanwhile, heat 4 tablespoons of olive oil in a sauté pan. Add the remaining sage leaves and shallots. Cook, stirring occasionally until the shallots are cooked through. Remove sage leaves.
Add the juice of the remaining lemon and cook for 3 – 4 minutes. Remove from heat and spoon over the chicken breasts.
