In a large bowl, mix together the spinach, cream cheese, water chestnuts, vegetable soup mix, mayonnaise and Cheddar cheese until well blended. Form into a ball, and roll in chopped walnuts. If the mixture is too soft to form a ball, refrigerate for about 30 minutes to set. Wrap the cheese ball in plastic wrap, and refrigerate overnight to blend the flavors before serving with your favorite crackers.
