1Heat oven to 350°F. In 9-inch square pan, heat butter and salt in oven 2 to 3 minutes or until bubbly. Stir in walnuts. Bake uncovered 5 minutes. Sprinkle with cheese; toss until walnuts are evenly coated. Bake 3 to 5 minutes longer or until cheese is light brown; cool.
2Into large bowl, tear lettuce, endive, radicchio and spinach into bite-size pieces (about 12 cups). Add dressing and walnuts; toss until greens are well coated.