Serves 16

  • 1 3/4 cups all-purpose flour
  • 3/4 cup Dutch-process cocoa powder
  • 1 cup packed dark brown sugar
  • 1 cup granulated sugar
  • 1 tsp. baking soda
  • 1 3/4 tsp. baking powder
  • 1 tsp. table salt
  • 1 egg
  • 2 egg yolks
  • 1 Tbsp. pure vanilla extract
  • 1/2 cup vegetable oil
  • 1 cup buttermilk, at room temperature
  • 1 cup boiling water
  • 1 Tbsp. espresso powder

    Sea Foam Frosting:
  • 3 egg whites
  • 1 cup plus 6 Tbsp. packed light brown sugar
  • 1 1/2 tsp. light corn syrup
  • 1/2 tsp. cream of tartar
  • Dash of table salt
  • 1 tsp. pure vanilla extract
  • Blue and green sanding sugar for decorating

    Preheat the oven to 350°. Grease a 13" x 9" x 2" pan with nonstick cooking spray or softened butter, line with parchment paper and grease again.

    For the cake: Add the flour, cocoa powder, brown sugar, granulated sugar, baking soda, baking powder 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, add the egg, egg yolks, vanilla, oil and buttermilk 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 a small bowl, 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. The batter will be quite thin.

    Pour the batter into the prepared pan and bake on the middle rack of the oven for 25 to 28 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. The cake can be made 1 day ahead and kept tightly wrapped in plastic wrap on the counter.

    For the frosting: Place a large heatproof bowl over a saucepan of simmering water over medium-high heat. Do not allow the bottom of the pan to touch the water. Add the egg whites, brown sugar, corn syrup, cream of tartar, salt and 5 tablespoons [75 ml] water. Using an electric hand mixer, beat the egg white mixture on high speed until stiff and glossy, about 7 minutes. Remove the bowl from the saucepan of hot water, add the vanilla, and continue beating for another 2 minutes.

    Generously frost the cake and sprinkle the top with sanding sugar. The frosted cake is best served within a few hours. The frosting dries and loses its "foamy" fluffiness pretty quickly but the cake can be kept, lightly covered, at room temperature for up to 3 days.

    Reprinted from The Vintage Baker by Jessie Sheehan with permission by Chronicle Books, 2018.

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