Soak the red onion slices in the 1/2 cup red wine vinegar to soften and take away some sharpness, about 30 minutes. Meanwhile, wash and dry the lettuces. Tear the leaves into bite-size pieces. In a large bowl, toss the greens with all but 3 tablespoons of the pine nuts, most of the scallions, half the cheese, half the prosciutto and all the basil and parsley. Arrange on a large platter.