Simmer chicken meat in water with peeled garlic cloves, salt and pepper for 45 minutes, or until tender. Drain and place chicken & garlic in large bowl; let stand until cooled (20-30 minutes.) Using hands, shred chicken. Using a spatula, fold in yogurt & olive oil until combined;
Gently fold in red onion & celery. Squeeze lemon wedge over chicken salad; add salt, pepper & red pepper (optional) to taste; fold in. Cover and let stand in fridge overnight. Serve on slices of whole grain bread garnished with walnuts.