Grill peach slices in a large heated grill pan for 2-3 mintes on each side until you have golden grill marks. Remove from pan.
Meanwhile, whisk vinaigrette ingredients in a small mixing bowl. Toss mache and red onion ingredients in a medium mixing bowl. On each salad plate, add mache rosettes, red onion, peaches, proscuitto and goat cheese crumbles. Drizzle with vinaigrette