Cut chickens into halves. Separate garlic cloves, peel and place in a small saucepan. Cover with boiling water for 1 minute, then drain. Cut the garlic into very thin slices. Toss half of the garlic in a small bowl with the parsley and olive oil. Add a bit of salt and pepper. Brush the garlic mixture onto the chicken halves. Transfer the chicken to a cookie pan, cover with plastic wrap and refrigerate until ready to use.
Heat the butter in a saucepan and add remaining garlic mixture. Add the lemon juice and season, to taste, with salt and pepper. Set aside to serve with chicken.
Set grids at medium or high. Preheat grill to medium heat. Grill the chickens 10 minutes per side or until internal temperature reaches 180°F. Serve chicken halves topped with the garlic sauce and parsley sprig. Serve with salad and vegetables.