Ingredients:

  • 1 box (15.25 oz) white cake mix
  • 1 cup water
  • 1/2 cup vegetable oil
  • 3 large eggs
  • 1 cup unsalted butter, softened
  • 4 cups powdered sugar
  • 2 tsp vanilla extract
  • 3 tbsp heavy cream
  • 1 pint fresh blueberries
  • 1 lb fresh strawberries, hulled and sliced

Instructions:

  1. Preheat the oven and grease a 9x13-inch baking pan.
  2. Combine the white cake mix, water, vegetable oil, and eggs. Beat on medium speed until the batter is smooth.
  3. Pour the batter into the prepared pan and bake until the edges just begin to pull away from the sides and the top is a pale golden hue.
  4. Allow the cake to cool completely in the pan before frosting.
  5. Cream the softened unsalted butter until pale and fluffy.
  6. Gradually add powdered sugar one cup at a time, mixing until incorporated.
  7. Mix in the vanilla extract and heavy cream until the frosting is velvety and holds a stiff peak.
  8. Spread a thick, even layer of frosting across the cooled cake using an offset spatula.
  9. Chill the frosted cake in the refrigerator for at least 2 hours to stabilize the frosting.
  10. Pat blueberries and sliced strawberries dry with paper towels to prevent juice bleeding.
  11. Arrange blueberries in a tight rectangle in the upper left corner for the stars.
  12. Create alternating horizontal rows of sliced strawberries and white frosting gaps for the stripes.
  13. Press each berry gently into the frosting to secure the decoration.