For Dressing: IN a screw-top jar, combine oil, walnuts, vinegar, chives, sugar, salt and pepper. Cover and shake well to mix. Set aside.
For Salad: IN a salad bowl, toss together lettuce, spinach, if using, watercress, and endive or radicchio. Shake dressing; drizzle over salad and toss gently to coat. Pass any remaining dressing with salad.