2egg whites (or roughly ⅓ cup pasteurized liquid egg whites)
Make the crust:
Preheat oven to 350° F. Have a 9-inch x 13-inch baking dish ready, and make sure there is room for it to go in your freezer.
Combine the graham cracker crumbs, ¼ cup of the sugar, and the melted butter in a large bowl. Stir thoroughly until the crumbs are coated with butter. Spread the mixture in the bottom of the baking dish. Use your fingers to firmly press the mixture down into an even layer.
Bake the crust for 12-15 minutes until it is lightly browned. Remove the pan from the oven and place it on a cooling rack. Allow the crust and pan to cool completely.
Make the filling:
Meanwhile, place the bowl and whisk attachment of a stand mixer into the freezer for 10 minutes. Remove the cherries and blueberries from the freezer and allow them to partially thaw while you whip the cream.
Assemble the chilled mixer bowl and whisk attachment onto the mixer. Pour the cold whipping cream into the bowl and turn the mixer on medium speed. Beat the cream until you see it just begin to thicken. Pause the machine to add ¼ cup of granulated sugar and the vanilla. Continue beating the cream until it is thick and has stiff peaks – stop beating as soon as you see this. Depending on how cold your cream and equipment are, and the speed of your mixer the cream should be ready anywhere from 2-5 minutes.
Spoon the whipped cream into a small bowl, cover with plastic wrap and hold it aside in the fridge. Wash and dry the mixing bowl and have a beater attachment ready.
Place the partially thawed fruit into the mixer bowl along with the remaining. sugar and the egg whites (or pasteurized liquid egg whites.) Beat these ingredients on high until stiff peaks begin to form - this can take anywhere from 5-10 minutes, so don't lose patience.
Gently fold the whipped cream into this fruit mixture - you do this gently to try to keep air in the mixture so it stays fluffy. Fold the two together just until they are combined.
Assemble the cake:
Spoon the filling onto the graham cracker crust, spreading it to an even layer. Cover the dish tightly with plastic wrap and place it in the freezer. Freeze the cake for about 4 hours.
When you're ready to serve: remove the plastic wrap and use a sharp knife to cut the cake into squares. Serve them immediately.
Adapted from a recipe in The Vermont Symphony Cookbook, 1984
The easiest way to make graham cracker crumbs is with a food processor or mini chopper, but you can also do this by hand: place the crackers in a bowl and use the bottom of a heavy glass or mug to crush them. Keep crushing until they become fine crumbs.
Homemade whipped cream is so much better than store bought, and sometimes folks worry about over-beating the cream. Make sure your bowl and beater or whisk attachment are very cold, and that your cream is very cold, too. Keep a close watch as you beat the cream, and stop the mixer as soon as you have stiff peaks.
This cake has the best consistency when enjoyed after about 3 to 4 hours in the freezer. The filling will hold but still be light and smooth. It will also delicious after a longer time in the freezer, but the filling will have an icier texture.
Store the cake wrapped in the freezer for up to 3 days.
The USDA states that there is a salmonella risk in consuming raw egg, especially for infants, young children, older adults, pregnant women, and people with weakened immune systems. If desired, pasteurized liquid egg whites can be used in place of the regular egg whites in this recipe.