1. In top of double boiler, combine water, grapenuts, tapioca, brown sugar, golden raisins and vanilla extract.
2. Cook over boiling water until mixture thickens, about 10 minutes, stirring constantly. Spoon into four 6-ounce custard cups or individual dessert dishes.
3. Using electric mixer at high speed, beat dry milk powder and ice water in small bowl until mixture is consistency of whipped topping.