For the cake: Preheat the oven to 350 degrees F. Spray a 9-inch nonstick springform pan with nonstick cooking spray.
In an electric mixer on high speed, beat the egg whites until soft peaks form. Add the granulated sugar slowly, then the vanilla, baking powder and salt while beating, about 2 more minutes. Fold in the ginger snaps and walnuts.
Transfer the batter to the prepared pan. Bake for 30 to 40 minutes. Let the cake cool for 15 minutes, then remove the springform.
For the frosting: In an electric mixer, beat the cream cheese, sour cream, powdered sugar and vanilla extract until soft peaks form and the mixture is smooth. Make sure the mixture has no lumps.
To assemble: Using an offset spatula, spread the frosting all over the cake. Garnish with the Sparkling Cranberries and serve.
Cook the agave nectar and 1/4 cup water in a saucepan over medium-low heat, 1 to 2 minutes. (Make sure not to let the syrup get too hot because the cranberries will pop.) Remove from the heat; stir in the cranberries. Cover and chill for 3 to 5 hours.
Line a baking sheet with parchment paper. Place the granulated sugar in a large bowl or baking dish. Drain the cranberries in a colander. Add 5 cranberries at a time to the sugar, gently tossing to coat. Place the cranberries in a single layer on the prepared baking sheet and let dry completely.
This recipe has been updated and may differ from what was originally published or broadcast.