This Mixed Berry Sheet Cake with Whipped Mascarpone Frosting has a spongy vanilla cake studded with fresh berries and is topped with a light and airy whipped mascarpone frosting.
Between the moist crumb, creamy whipped topping, and pops of fresh fruit, this cake manages to be both light and satisfying.
Cake Flour – Cake flour contains less protein than all-purpose flour, resulting in a moister and fluffier cake that makes it worth having this ingredient on hand. Cake flour is made by combining flour and starch, often corn starch. It can be found in most grocery stores. If you want to make it yourself, simply measure out 1 cup of all-purpose flour, remove 2 tablespoons of flour and replace it with 2 tablespoons of cornstarch. Stir well to combine.
Dairy & Eggs – Make sure that your milk, sour cream, and egg whites have a chance to come up to room temperature before you begin mixing everything together. Allowing these ingredients to come to room temperature makes for a smoother batter. And, of course, be sure to allow the butter to soften before combining it with the sugar.
Mixed Berries – In this version, I used strawberries and blueberries but you can use whatever berries you like. Raspberries and blackberries would be delicious! You’ll notice that I cut the strawberries to be about the same size as the blueberries, which I left whole. Making the berries roughly the same size will provide more consistency throughout the cake.
Mascarpone Cheese – This addition to the whipped frosting not only lends to a more rounded flavor but also helps to stabilize the frosting. Often, whipped topping will fall and start to melt fairly quickly. By adding mascarpone cheese to the mix, the frosting maintains its structure.
Step By Step Instructions
Preheat the oven to 350°F and prepare an 11x15x2 cake pan by greasing it with butter.
In a bowl, combine the flour, baking powder, and salt.
In a large liquid measuring cup, measure the milk. Then stir in the sour cream, egg yolks, and vanilla.
In a large bowl, with an electric hand mixer, cream together the sugar and softened butter. Make sure they are well incorporated, mixing for about 2 minutes.
Begin by adding 1/3 of the flour mixture to the butter mixture, whisking only until just combined.
Then, add half of the milk mixture.
Continue with another 1/3 of the flour.
Then, the other half of the milk.
And finally, finish with the last 1/3 of flour, stirring just until combined.
To the berries, add about 1 tablespoon of cake flour and toss to coat. Then, gently fold the berries into the batter.
Transfer the batter to the prepared cake pan and smooth out the top.
Bake for 35 to 40 minutes, until a toothpick comes out clean and the top is very lightly golden.
Allow the cake to cool for at least 2 hours before frosting.
Once the cake is completely cool, prepare the frosting by creaming together the heavy cream, mascarpone cheese, powdered sugar, and vanilla until it is a smooth whipped consistency and stiff peaks have begun to form.
Spread the whipped topping over the cake. I used some of the blueberries and strawberries to make a 4th of July flag cake, but you can decorate however you like!
How to Store Leftovers
Leftovers of this cake, if you have any, should be kept covered in the fridge for up to 3 days.
Pull the cake from the fridge about 20 minutes before you want to serve it.
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Mixed Berry Sheet Cake with Whipped Mascarpone Frosting
- 3 cups cake flour plus 1 tablespoon for the berries
- 4 teaspoons baking powder
- 1/2 teaspoon salt
- 1 1/2 cups granulated sugar
- 1 cup (2 sticks) unsalted butter softened
- 1 cup whole milk room temp
- 1/2 cup sour cream room temp
- 6 egg whites room temp
- 1 teaspoon vanilla
- 2 cups mix of fresh berries cut larger berries to be equal in size to smaller berries
- 16 ounces heavy cream
- 8 ounces mascarpone cheese
- 1 cup powdered sugar
- 1 teaspoon vanilla
Make the Cake
- Preheat oven to 350°F. Prepare an 11x15x2 sheet cake pan by thoroughy greasing the bottom and sides with butter.
- In a medium bowl, mix together the cake flour, baking powder, and salt. Set aside.
- Whisk together the milk, sour cream, egg whites, and vanilla. Set aside.
- In a large bowl, using a hand mixer, cream together the sugar and softened butter until well combined.
- Add 1/3 of the dry ingredients to the butter-sugar mixture and mix just until combined.
- Add 1/2 of the milk mixture and stir until just combined.
- Continue with another 1/3 of the dry ingredients, mixing just until combined.
- Stir in the other half of the milk mixture.
- Mix in the last 1/3 of the dry ingredients until just combined.
- Add the tablespoon of flour to the fruit and toss. Then, using a spatula, gently stir them into the cake batter.
- Spread the cake batter into the prepared cake pan. Bake at 350°F for 35 to 40 minutes, until a toothpick comes out clean. Allow to cool completely, at least 2 hours, before frosting.
Make the Frosting
- In a large bowl, add all of the frosting ingredients. Using an electric hand mixer, whip until stiff peaks form.
- Spread the frosting over the cooled cake.
- Optional: Decorate with additional fruit.
- This cake can be made the day before you plan to serve it and the frosting will remain fluffy and creamy.
- Store the cake in the refrigerator. It will be good for up to 3 days.
- You can subsititute frozen berries without needing to thaw them first. Simply toss them in the flour and mix them into the batter just as you would fresh fruit.