Ingredients
Scale
- 1 tablespoon butter, for the pan
- 1/3 cup all-purpose flour
- 1/3 cup unsweetened cocoa powder
- 1/4 teaspoon salt
- 4 large eggs, separated
- 1 teaspoon vanilla extract
- 3/4 cup plus 3 tablespoons confectioners’ sugar
- 1 cup heavy cream
- 1 tablespoon sour cream
- Optional: Chocolate Ganache topping
Instructions
- Heat oven to 350° F. Butter a 9-by-13-inch jelly roll pan and line with parchment; butter the parchment.
- Whisk together the flour, cocoa, and salt in a small bowl.
- Beat the egg yolks, vanilla, and ¼ cup of the sugar in a medium bowl with an electric mixer on medium-high until light yellow, 3 to 4 minutes.
- In a separate bowl, beat the egg whites (with clean beaters) on medium-high until foamy, 1 to 2 minutes. Gradually add ½ cup of the remaining sugar and beat until stiff peaks form, 2 to 3 minutes more.
- Gently fold the egg yolk mixture into the egg whites. Gradually fold in the dry ingredients.
- Transfer the mixture to the prepared pan and use an offset spatula to smooth the surface. Bake until the cake springs back lightly when pressed, 8 to 10 minutes. Remove from pan.
- Sprinkle cocoa powder on clean towel that is roughly 9×13. Transfer cake parchment-side up to towel. Peel back parchment and discard. Carefully roll up cake in towel to cool completely.
- Whip the heavy cream, sour cream, and the remaining 3 tablespoons of sugar in a medium bowl with an electric mixer on medium-high until stiff peaks form, 1 to 2 minutes.
- Unroll the cake. Spread the whipped cream on the cake, leaving a 2-inch border along one of the short ends. Starting at the other short end, roll up the cake toward the uncovered border (letting the parchment fall away as you roll). Place the cake seam-side down on a serving platter.
- Optional: Drizzle the chocolate ganache over the top; let set for 5 minutes.