Stir vinegar into E. Milk until slightly thickened. Blend in salad dressing, mustard, horseradish, and salt; chill. Layer vegetables and ham in 4-quart salad bowl as follows: lettuce, mushrooms, tomatoes, ham, onion, peas and cucumber. Spread dressing over top of salad. Cover. Chill several hours. Garnish to serve. Makes 6 to 8 servings.