Wash and stem grapes; drain. In large mixing bowl, combine sugar, sour cream, cream cheese, and vanilla till smooth. Pour over grapes; mix till thoroughly combined. In separate bowl, mix nuts and brown sugar together. (I use the maximum amount of brown sugar, because I love the mix of the flavor with the sweet/sour of the grapes.) Pour grape mixture into serving dish; sprinkle top with sugar and nut mixture. Chill and serve. This recipe makes a very large portion (suitable for a family gathering of 20 or possibly more, depending on appetites). Recipe may be halved. Keeps well in refrigerator for several days (if it lasts that long).

Warning: This stuff is addictive!