Bake and cool any 9×13-inch quarter sheet cake, whatever flavor you enjoy with vanilla frosting and berries. You can follow steps 1–4 for making my vanilla sheet cake, which is the cake pictured. Cool cake completely before decorating.

With a handheld or stand mixer fitted with a paddle attachment, beat the butter on medium speed until creamy, about 2 minutes. Add confectioners’ sugar, heavy cream, and vanilla extract. Beat on low speed for 30 seconds, then increase to medium-high speed and beat for 4 full minutes. Add up to 1/4 cup more confectioners’ sugar if frosting is too thin or another Tablespoon of cream if frosting is too thick. Add a pinch of salt if frosting is too sweet. (I add 1/8 teaspoon salt.) Frosting should be extra fluffy.

Spread 2/3 of the frosting all over the cake (I use and recommend an offset spatula), reserving the remaining 1/3 for piping detail. Place whole fresh blueberries and halved fresh strawberries to mimic the stars and stripes on an American flag. Using a piping bag (disposable or reusable) and piping tips, fill in the space between the stars and stripes. I used Ateco 32 piping tip for the piping between the blueberry “stars” and Ateco 844 piping tip for the piping between the strawberry “stripes.”

Slice and serve. Cover leftover cake tightly and store in the refrigerator for up to 5 days.