- 2¼ cups cake flour
- 1½ cups sugar
- 1 tablespoon baking powder
- 1 teaspoon salt
- ½ cup softened, unsalted butter
- 1 cup whole milk
- 1½ teaspoons vanilla extract
- 2 eggs
- ⅓ cup shrub
- 1 envelope unflavored gelatin
- ⅔ cup hot water
- 1½ cups cream
- ¼ cup mascarpone cheese
- 2-3 tablespoons confectioners' sugar
- 2 cups thinly sliced strawberries
- 1 cup blueberries
To make the cake, preheat the oven to 350 degrees.
Butter and flour a 13X9 sheet cake pan.
In a medium mixing bowl, sift together flour, sugar, baking powder and salt. Add butter, ⅓ cup milk and vanilla. Beat on medium speed for 2 minutes. Add egg and remaining milk. Beat 2 minutes more. Pour batter into the prepared pan and bake for 25 to 28 minutes until the top is golden and a toothpick inserted in the middle comes out clean.
Remove cake from oven. Cool completely. Use a skewer to poke holes all over the cake at ½-inch intervals. Pour shrub into a small bowl and sprinkle gelatin over it. Let sit five minutes. Whisk in hot water. Slowly pour the mixture over the cake, taking care that a little bit seeps down into each poked hole. Chill the cake for at least 4 hours.
To frost the gelled cake, beat cream until it gets soft peaks, about 60 to 90 seconds. Add mascarpone and sugar and beat until the cream holds stiff peaks, another 60 seconds. Spread the cream in an even layer over the top of the cake. Decorate the cake with the berries to resemble an American flag, with the blueberries as stars and the strawberries as stripes.