Yule Log Cake

Step 1
Preheat the oven to 355 degrees F (180 degrees C). Grease a jelly roll pan. Line it with parchment paper, and grease the paper.

Step 2
Beat 1/2 cup plus 2 tablespoons sugar and egg yolks until light and fluffy. Add 3/4 cup plus 1 tablespoons flour, butter, lukewarm water, and baking powder; beat until well combined.

Step 3
Beat egg whites and salt in a glass, metal, or ceramic bowl until stiff. Transfer 1/3 of the whites to the cake batter and gently fold in. Repeat with remaining whites. Spoon batter into the prepared pan and spread evenly.

Step 4
Bake in the preheated oven until it springs back when pressed gently in the middle, about 12 minutes. Remove from the oven and let sit in the pan for 3 minutes, before carefully turning the cake out onto a large piece of parchment paper. Roll the parchment and cake from one short end to the other and let cool.

Step 5
While the cake is cooling, place chocolate for buttercream in the top of a double boiler over simmering water. Stir frequently, scraping down the sides with a rubber spatula to avoid scorching, until chocolate is melted, about 5 minutes. Remove from the heat.

Step 6
Beat softened butter in a bowl until light and creamy. Add powdered sugar in small increments, beating between each addition. Add melted chocolate and beat until well combined.

Step 7
Carefully unroll the cooled sponge cake. Spread a thin layer of buttercream across the top to the edges. Firmly roll back up, using parchment to help you, into a tight roll.

Step 8
At one end of the roll, cut off a diagonal slice to represent a branch, about 2 inches in length at the longest side. Frost the entire roll with buttercream. Use a palette knife to create uneven ridges to represent tree bark. Position the branch somewhere near the center of the log and cover with buttercream.

Step 9
Drag the tines of a fork lengthwise across the buttercream to create an extra bark effect. Dust the entire log with cocoa powder.