For the cake:
24 ounces frozen strawberries, thawed
¼ cup milk, at room temperature
6 large egg whites, room temperature
1 tablespoon vanilla extract
2¼ cups cake flour, sifted
1¾ cups sugar
4 teaspoons baking powder
1 teaspoon salt
12 tablespoons unsalted butter (1½ sticks), softened
For the filling:
1 cup plus 1 tablespoon champagne, prosecco or other sparkling wine
2 sticks (1 cup) butter, softened
2½ cups confectioners’ sugar
I made a recipe and a half of the cake in order to get three 6-inch cakes, with some batter leftover. The amount of buttercream you need will depend on whether you’re just filling or filling and frosting the cake. I filled mine with the champagne buttercream and frosted with my favorite swiss meringue buttercream. I got the idea for the ruffle cake from My Sweet and Saucy, and her video tutorial shows you how to make the ruffled design.
Start by making the strawberry purée. Pour thawed strawberries into a fine mesh strainer set over a large bowl to remove any liquid. Save liquid for a later use or discard. Purée strawberries in a blender or food processor and set aside ¾ cup for the cake. The remaining ½ cup can be used to fill the cake, top ice cream, make daiquiris or almost anything else you can think of.
To make the cake, heat oven to 350º. Butter and flour two 8-inch pans and line each with a parchment round. In a small bowl, whisk together ¾ cup of strawberry purée, milk, egg whites and vanilla. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, combine flour, sugar, baking powder and salt on low speed. Add butter and continue mixing until the mixture resembles coarse crumbs. Add the purée mixture and beat at medium speed until smooth, scraping down the sides and bottom of bowl as needed. Divide the batter evenly among the pans (a kitchen scale works wonders here) and smooth tops with a rubber spatula.
Bake cakes for about 25 minutes, or until a toothpick inserted in the center comes out clean. Cool cakes in pans for 10 minutes, then turn onto a wire rack to cool completely.
While the cakes are cooling, prepare the filling. Place 1 cup of champagne in a small saucepan set over medium-high heat. Simmer for about 10 minutes, or until champagne has been reduced to 2 tablespoons. Pour into a small bowl and allow to cool.
In the bowl of a stand mixer fitted with the paddle or whisk attachment, beat butter and sugar together on low speed, gradually increasing to medium-high. Beat until butter is lightened and the frosting is thick and fluffy. Add the reduced champagne and the remaining 1 tablespoon of champagne and continue beating until incorporated.
Fill and frost the cake as desired.