Grapes and Sour Cream

2 - 2 1/2# green, seedless grapes
1/2 pt. sour cream
8 oz. cream cheese
1/3 C. sugar
2 t. vanilla
Dark brown sugar

Mix sour cream, cream cheese, sugar, and vanilla until smooth. Add grapes and mix well. Put in glass bowl and cover heavily with brown sugar. Chill at least 2 hours, but not overnight.