Wash the lettuce, arugula, frisee, watercress and radicchio thoroughly and let them dry (or dry with paper towels. Tear the greens and place them into a bowl. Add the onion, mild greens, carrots and tomatoes if desired. Toss to distribute the ingredients evenly. Just before serving, prepare one of the dressings and pour as much as desired over the greens. Toss, let rest for 5-10 minutes and serve. Makes about 10 servings