Chocolate Birthday Sheet Cake with Strawberry Marshmallow Frosting

Yes, I know: you’re a tiny bit upset with me that I did not share this cake a few days ago when you all would have immediately dropped everything to make it for your valentine. Pink frosting does indeed scream Valentine’s Day, I agree. But here’s the thing: this cake is so easy (you only really need to dirty a single bowl) and so tasty – think uber moist and deeply chocolate-y – and the frosting, flavored with a simple purée, is the lightest, most marshmallow-y, most addictive item to spread on a cake (or to spoon into your mouth) I’ve come across in quite a while (sorry American buttercream, my first true love). In other words, I’m suggesting you drop everything and make it immediately despite the passing of everyone’s favorite (or, not so favorite) mid-February holiday. And if strawberry is not your thing, by all means omit it and you will have before you the chocolate and marshmallow Hostess Suzy-Q cake of your dreams. The recipe can be found here on Food52, where it was originally published, and on my blog.


To take a peek at the original blog post for my chocolate birthday sheet cake with strawberry marshmallow frosting, and to peruse my collection of original recipes, click here.




For the cake:

  • 2 cups cake flour, sifted
  • 3/4 cup Dutch-process cocoa powder
  • 1 cup packed light brown sugar
  • 1 cup granulated sugar
  • 1 3/4 tsp baking powder
  • 1 tsp baking soda
  • 1 tsp table salt
  • 1 egg, room temperature
  • 2 egg yolks, room temperature, save the whites for the frosting
  • 1 Tbsp pure vanilla extract
  • 1/2 cup vegetable oil
  • 1 cup sour cream, room temperature
  • 1 cup boiling water
  • 1 Tbsp espresso powder

For the frosting:

  • 1 cup sliced strawberries, plus more for decorating
  • 2 egg whites
  • 1/2 cup, 2 Tbsp granulated sugar
  • 1/4 tsp cream of tartar
  • 1/4 cup light corn syrup
  • 1/8 tsp salt
  • 1 1/2 tsp lemon juice, or more to taste
  • Red gel food coloring, optional
  • Pink sparkling sugar for decorating, optional
  • Strawberry ice cream for serving, optional



Preheat the oven to 350°F. Grease a 13-by-9- by-2-in pan with nonstick cooking spray or softened butter and line with parchment paper.

For the cake, add the flour, cocoa powder, brown sugar, granulated sugar, baking powder, baking soda, and salt to the bowl of a stand mixer fitted with the paddle attachment; mix on low speed until well combined.

In a small bowl, or in a large 4-cup liquid measuring cup (my preference), add the egg, egg yolks, vanilla, oil, and sour cream and whisk until combined. With the mixer on medium-low speed, slowly pour the wet ingredients into the dry ingredients.

Beat until incorporated, scraping down the bowl with a rubber spatula as needed. In the same small bowl/measuring cup, no need to clean it, combine the boiling water and espresso powder and add to the batter in the mixer bowl.

Mix again on medium speed for 30 seconds, until smooth, scraping the bowl with a rubber spatula as needed. The batter will be quite thin.

Pour the batter into the prepared pan and bake for 28 to 32 minutes, rotating at the halfway point. The cake is ready when a toothpick inserted in the middle comes out with a moist crumb or two. Let cool completely in the pan. Or let cool enough so you can comfortably handle it, and invert the cake on to a serving plate to continue cooling.

To make the frosting, in a food processor fitted with the metal blade, or in a blender, process the berries until pureed. Place a sieve over a small bowl, pour the puree into the sieve, and using a rubber spatula, press the puree through the sieve to remove the seeds. Set aside.

Add the egg whites, sugar, corn syrup, cream of tartar, and salt in the now-cleaned bowl of the stand mixer and nestle it in a saucepan of simmering water over medium-high heat. Do not allow the bottom of the bowl to touch the water. Whisk until the mixture is just warm to the touch.

Remove the bowl from the heat, add the puree and transfer it to the stand mixer fitted with the whisk attachment. Mix on high speed until stiff and glossy, about 7 minutes. Add the lemon juice and whisk a final time to combine.

Once the cake is cool, generously frost it and sprinkle the top with pink sanding sugar. The frosted cake is best served within a few hours with a few sliced strawberries on each plate – or, a scoop of strawberry ice cream – I mean this is a birthday cake, after all.

The frosted cake is best eaten the day it is made.




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