- Preheat the oven to 350 F degrees.
- Butter and flour an 18 x 13 x 1-½” sheet pan . . . I used a 17 x 11″ baking pan and just baked it longer.
- On high speed, cream the butter and sugar in a large bowl with a mixer, until light and fluffy.
- On medium speed, add 2 eggs at a time, mixing after each addition.
- Add sour cream and vanilla, mix thoroughly, scraping down the sides of the mixing bowl.
- With a whisk, in another large bowl, mix the flour, corn starch, salt and baking soda.
- On low speed, mix the flour mixture into the butter mixture until well blended.
- Pour the cake batter into the prepared cake pan.
- Spread the cake batter evenly in the pan.
- Bake in the center of the oven for 40 – 50 minutes (if you use the smaller pan as I did). If you use a larger sheet pan, bake for only 20 – 30 minutes. Make sure that a toothpick comes out clean.
- Allow the cake to cool completely!
- Combine the butter, cream cheese/mascarpone cheese, sugar and vanilla in a medium bowl using an electric mixer.
- Mix until smooth.
- Spread the icing all over the cake and smooth it out flat.
- Decorate the cake with blueberries for the ‘stars’ portion of the flag.
- Place the raspberries in straight lines for the ‘stripes’ portion of the flag
*Note: If you don’t serve this cake immediately, keep the cake refrigerated due to the amount of butter in the icing that will melt. Remove the cake to come back to room temperature before serving.
This recipe is based on Ina Garten’s flag cake with many changes of my own indicated in parentheses.