Amerikai zászlós torta

Ingredients for the cake (makes 20-24 servings):

18 tablespoons unsalted butter at room temperature
3 cups sugar
6 extra-large eggs at room temperature
1 cup sour cream at room temperature
1 1/2 teaspoons pure vanilla extract
3 cups flour
1/3 cup corn-starch
1 teaspoon salt
1 teaspoon baking soda

Ingredients for the icing:

450 gr unsalted butter at room temperature
680 gr pounds cream cheese at room temperature
450 gr pound confectioners’ sugar, sifted
1 1/2 teaspoons pure vanilla extract

To assemble:

500 ml blueberries
700 ml strawberries or raspberries

Preparation:

1. Heat the oven to 180 degrees C°.
2. Butter and flour a 46cm x33cm x 4cm sheet pan.
3. Cream the butter and sugar in the bowl of an electric mixer, fitted with the paddle attachment on high speed, until light and fluffy. On medium speed, add the eggs, 2 at a time, then add the sour cream and vanilla. Scrape down the sides and stir until smooth.
4. Sift togetherthe flour, cornstarch, salt, and baking soda in a bowl. With the mixer on low speed, add the flour mixture to the butter mixture until just combined. Pour into the prepared pan. Smooth the top with a spatula. Bake in the center of the oven for 20 to 30 minutes, until a toothpick comes out clean. Cool to room temperature.
5. For the icing, combine the butter, cream cheese, sugar, and vanilla in the bowl of an electric mixer fitted with the paddle attachment, mixing just until smooth.
6. Spread three-fourths of the icing on the top of the cooled sheet cake. Outline the flag on the top of the cake with a toothpick. Fill the upper left corner with blueberries. Place rows of strawberries (or raspberries) across the top of the cake, like a red stripe. Put the remaining icing in a pastry bag fitted with a star tip and pipe two rows of white stripes below the raspberries. Alternate rows of red berries and icing until the flag is completed.
7. You can serve this cake right in the pan. If you want to turn it out onto a board before frosting, use parchment paper when you grease and flour the pan.