To make this white chocolate fudge recipe, combine sugar, sour cream and butter in a large sauce pan. Bring to the boil, stirring constantly. Continue boiling 7 minutes over medium heat or until candy thermometer reaches 234 degrees F. Stir constantly to prevent scorching. Remove from heat. Add white chocolate and stir until melted and smooth. Stir in Solo Marshmallow Creme and chopped walnuts until well blended. Pour into a greased baking pan. Cool at room temperature. Cut white chocolate fudge into squares. Makes 2 1/2 pounds.