Fold a 24-inch piece of foil in half lengthwise. Fit around a 1-quart souffle dish to create a 3-inch collar above the dish. Secure tightly with tape.
Cook blueberries, sugar and 1 tablespoon water in saucepan over medium heat for 6 minutes, breaking up with a spoon. Add cornstarch mixture; cook 1 more minute. Cool completely.
In a medium-size bowl, mix together the powdered egg whites and warm water. Let stand for 5 minutes. Beat on medium-high speed until soft glossy peaks form.
In a large bowl, mix together softened ice cream and whipped topping; ice cream should be consistency of sour cream (do not let it melt). Fold in the beaten egg whites. Swirl in blueberry mixture and raspberries.
Spoon mixture into the prepared dish. Freeze for 6 hours to overnight. To serve, let stand 10 minutes at room temp.