Yule Log Cake

Preparation

Cake

1. Prepare a jelly-roll pan or heavy 10- by 15-inch sheet pan by lining with parchment paper. Sift the flour and cocoa together onto a sheet of waxed paper, then use the paper to transfer the mixture back into the sifter. Reserve. Preheat the oven to 350⁰F.
2. Whisk the eggs and sugar together in a large mixer bowl. Place that bowl into a bowl of hot water and warm the eggs to approximately 100⁰F. Stir frequently to avoid cooking the eggs.
3. When the eggs are warm, remove the mixing bowl from the water and attach to a mixer fitted with a whip attachment. Add the vanilla and whip the egg and sugar mixture at medium speed until it has tripled in volume.
4. Sift the flour and cocoa mixture over the surface of the egg mixture, and quickly but gently fold the flour into the egg mixture with a rubber spatula. Be careful not to deflate the batter.
5. Pour the melted, cooled butter around the edges of the batter and fold in quickly.
6. Spread the batter immediately onto the parchment paper-lined sheet pan. Bake until light brown and springy to the touch, approximately 10 minutes. Transfer the cake to a rack by lifting out the edges of the parchment paper. Sift powdered sugar over the top of the cake layer, place a clean kitchen towel on top, and gently, loosely roll the layer, starting from the 10 inch side. Carefully peel the parchment paper off as you roll. Let the cake cool to room temperature. The cake can be covered tightly with plastic wrap and reserved for up to a day before filling.

Pastry Cream

1. Whisk the unbleached flour, sugar and 1/2 cup of the milk in a medium bowl. Place the remaining 1 1/2 cups milk in a medium saucepan with a heavy bottom and place over medium heat. Bring to a boil, and just as it starts to bubble, turn to medium-low. Whisk about 1/3 of the hot milk into the egg yolk mixture, then quickly whisk the egg yolk mixture into the hot milk in the pan. Cook, whisking, until the mixture becomes quite thick and starts to boil. Whisk in the butter and vanilla. Transfer the pastry cream to a bowl and cover the surface with plastic wrap. Chill until completely cold.

Frosting

1. For the frosting, place the softened butter in a large bowl or stand mixer, and beat until smooth. Add the powdered sugar and cocoa and beat on low to mix. Beat in the half and half a tablespoon at a time, scraping down and mixing until a fluffy texture is achieved. If necessary, beat in another tablespoon of half and half to make a creamy, spreadable frosting.
2. To assemble, choose a platter or pan to place the finished cake on, and dust it with powdered sugar. Carefully unroll the cake on the counter. Spread the pastry cream over the cake, starting at the edge closest to you leaving two inches of the far outer edge bare. Carefully roll up the cake, starting at the side closest to you, then place on the platter. Spread the frosting over the cake, using a spatula to create long strokes along the length of the cake. Use a fork to create bark textures in the frosting. Chill the cake for easier slicing. Dust with powdered sugar before serving. The cake keeps, covered, for up to four days.