Combine sugars, and sour cream in a small Saucepan. Cook over medium high heat, Stirring until it boils. Continue to boil until mixture reaches soft ball stage. Stir in salt and vanilla. Pour hot mixture over walnuts in a large mixing bowl. Mix until nuts are evenly coated. Spoon onto wax paper. Separate walnuts--Allow to cool and set--When dry store in airtight container.