
10 egg whites
1⅔ cups butter
¾ cup sliced fresh strawberries
¾ cup fresh raspberries
½ cup plus 3⅓ cups granulated sugar, divided
Nonstick cooking spray
All-purpose flour
5 cups cake flour
1½ tablespoons baking powder
1⅔ cups Champagne
3 tablespoons vegetable oil
4 teaspoons vanilla extract
12 drops red food coloring
1 recipe Champagne Buttercream