French Chocolate Bûche de Noël (Yule Log) Cake

Make the Cake - Gather the ingredients.

Make the Cake - Preheat the oven to 400 F.

Make the Cake - Grease a 10 x 15-inch rimmed baking sheet or jelly roll pan and line it with parchment paper.

Make the Cake - Grease the parchment or spray it with cooking spray. Set the pan aside.

Make the Cake - Beat the eggs in the bowl of an electric mixer fitted with a whisk attachment until thick and foamy, about 5 minutes.

Make the Cake - Add the sugar, vanilla extract, and salt to the eggs and continue beating for 2 minutes.

Make the Cake - Carefully fold the flour, 2 to 3 tablespoons at a time, into the eggs. Once the flour is incorporated, stop mixing. Do not overmix or the cake will be tough.

Make the Cake - Gently spread the batter into the prepared pan. There will be peaks in the batter; gently smooth them with a spatula, but do not press the batter down.

Make the Cake - Bake the cake until the top springs back when gently pressed and the edges pull away from the pan, about 10 minutes.

Make the Cake - Invert the baked cake onto a clean, dry kitchen towel and peel off the parchment paper.

Make the Cake - Let stand for 3 minutes and then lightly score the length of one short side of the cake, leaving a 1-inch border, taking care not to cut through the cake.

Make the Cake - Fold the scored end of the cake in toward the center and then gently continue to roll the cake, wrapped in the towel.

Make the Cake - Transfer to a rack, seam-side down and cool completely in the towel.

Make the Cake - While the cake cools, make the buttercream.

Make the Chocolate Buttercream - In a clean, dry mixing bowl with a whisk attachment, beat the egg whites on high speed until soft peaks form. Set aside.

Make the Chocolate Buttercream - In a small saucepan, bring the sugar and 2/3 cup water to a boil.

Make the Chocolate Buttercream - Allow sugar-water mixture to boil until it has reduced to a thickened syrup consistency.

Make the Chocolate Buttercream - Begin beating the egg whites on high speed again, and with the motor running, slowly pour the hot sugar syrup into the eggs in a steady stream.

Make the Chocolate Buttercream - Pour the melted chocolate, espresso powder, and vanilla extract into the egg whites and continue beating until the meringue has cooled completely, about 5 minutes.

Make the Chocolate Buttercream - Add the softened butter to the meringue, 2 tablespoons at a time, while beating on high speed until all of the butter is incorporated.

Make the Chocolate Buttercream - If the buttercream becomes runny during this process, refrigerate the meringue until it has chilled through.

Make the Chocolate Buttercream - Continue the process of beating the butter into the meringue.

Assemble the Chocolate Yule Log - Unroll the cake and set aside the towel.

Assemble the Chocolate Yule Log - Evenly spread 2 cups (or your desired amount) of the chocolate buttercream on the inside of the cake, spreading in the direction of its natural curve, leaving a 1-inch border around the edges.

Assemble the Chocolate Yule Log - Gently roll it back into a log.

Assemble the Chocolate Yule Log - Trim the rough ends of the roll. Then cut off about 1/4 of one end of the cake roll on the diagonal. Reattach it to the center of the cake with some buttercream to resemble a 'branch' protruding from the Yule log.

Assemble the Chocolate Yule Log - Spread the remaining buttercream over the bûche de Noël to cover it. Gently drag a butter knife or a small offset spatula through the frosting to give the appearance of rough tree bark.

Assemble the Chocolate Yule Log - Add a Père[meringue mushrooms](https://www.thespruceeats.com/meringue-mushrooms-520686) to complete the festive look.

Assemble the Chocolate Yule Log - Chill the cake before serving it to allow the buttercream to set. Before serving, dust with confectioners' sugar and/or cocoa powder, if you like. Refrigerate any leftovers.

Assemble the Chocolate Yule Log - Serve and enjoy.