Ingredients
3/4 cup all-purpose flour
1/4 cup unsweetened cocoa powder
1 teaspoon baking powder
1 teaspoon salt
3 extra-large eggs
1 cup granulated sugar
1/3 cup water
1 teaspoon vanilla extract
12 tablespoons (or 1 1/2 sticks) unsalted butter, room temperature
4 1/2 cups confectioners’ sugar
1 1/2 teaspoons vanilla extract
2 tablespoons whole milk
1 stick unsalted butter, room temperature
3 cups confectioners’ sugar
1 teaspoon vanilla extract
3 tablespoons unsweetened cocoa powder
2 tablespoons whole milk
Instructions
  1. For the cake: Preheat the oven to 375 degrees F. Spray a jelly roll sheet pan (10 x 15-inch) with nonstick cooking spray. Line the pan with parchment paper—leave enough for an overhang to help get the cake out after baking—and spray with cooking spray again. Set aside.

  2. In a medium size bowl, sift together the flour, cocoa powder, baking powder, and salt. Set aside.

  3. Place eggs in a stand mixer fitted with a whisk attachment and mix on high speed until eggs are thick and a light yellow in color.

  4. Slowly add in sugar and whip for 4-5 minutes, until the sugar dissolves and creates volume in the egg mixture. Then, add the water and vanilla extract on low speed.

  5. Slowly add the flour mixture and continue to mix until combined. Do not over-beat.
 Pour mixture into pan, making sure to cover every inch of the pan. Tap the pan against the counter a few times to release any air bubbles.

  6. Bake cake for 13-15 minutes or until a toothpick inserted comes out clean.
 While the cake is baking, sift a good amount of confectioners’ sugar onto a clean dish towel, covering every inch of the towel evenly.

  7. When the cake is finished baking, remove from the oven and use a paring knife to cut along the side of the edges. While the cake is still hot, flip the pan over onto the clean dish towel with the confectioners’ sugar. Carefully remove the parchment paper and roll the cake with a dish towel from one short end to the other short end. Allow to cool for 45 minutes or until cooled completely. 

  8. For the vanilla buttercream: Combine all ingredients in a stand mixer on low speed and mix until combined. 

  9. Scrape down the sides of the bowl. Increase speed to high and mix for 5 minutes, or until the buttercream is fluffy and white in color. Transfer 1 cup of buttercream to a pastry bag with a large star tip. Set aside.

  10. For the chocolate buttercream: Combine all ingredients in a stand mixer on low speed and mix until combined.

  11. Scrape down the sides of the bowl. Increase speed to high and mix for 5 minutes, or until the buttercream is fluffy. Set Aside.

  12. For the assembly: Unroll cooled cake and place vanilla buttercream on the inside of the cake, leaving a 1-inch border around the edges. The vanilla buttercream should measure ½-inch in height. 

  13. Carefully remove the dish towel, and roll the cake. 
Place the cake, seam side down, onto a sheet pan lined with parchment paper.

  14. Place the cake in the refrigerator and allow it to set for 20 minutes.

  15. Remove the cake from the refrigerator and cover the outside with the chocolate buttercream using an offset spatula (the back of a spoon or a butter knife are good substitutes). Covering the bottom of the cake with the chocolate buttercream is entirely optional.
  16. Use the spatula to create designs on cake. Transfer to the refrigerator and allow to set for 20 minutes.

  17. Remove the cake from the refrigerator and begin to decorate the top of the cake with the pastry bag with the star tip filled with the reserved vanilla buttercream. Pipe 4 rows of dollops on the top center of the cake going lengthwise down the cake.

  18. Using a vegetable peeler or a grater, shred milk or dark chocolate over the vanilla buttercream dollops.
 Gold leaf is optional.
  19. Refrigerate until ready to serve and then allow to sit at room temperature for an hour before consuming. 
It’s best eaten the day it’s made.