Use a sharp knife to slice each chicken breast in half horizontally to make 8 thin pieces. Place the chicken on a greased baking sheet and cook under a preheated hot grill for 2 minutes.
Turn the chicken over and drape a slice of prosciutto over each piece. Return to the grill for a further 2 minutes until the prosciutto begins to crisp. Place a sage leaf on top of each and cook for a further 1 minute until the chicken is cooked through and the prosciutto and sage are crisp. Serve with green beans and new potatoes.