Chocolate Yule Log

Instructions

• Make the buttercream filling: Whip powdered sugar, butter, coffee-flavored liqueur, cocoa powder, salt together in the bowl of a stand mixer fitted with the whisk attachment on high speed.
• Transfer filling mixture to a separate bowl and add mascarpone cheese. Mix until combined; set aside. Clean and dry the stand mixer bowl.
• Preheat the oven to 400 degrees F (200 degrees C).
• Prepare a 13x18-inch rimmed sheet pan for the sponge cake: Brush a little melted butter over the sheet pan, then line the pan with parchment paper, and brush remaining melted butter on top.
• Whisk cocoa powder, flour, and salt together in a bowl, making sure to break up any clumps.
• Place eggs in the clean bowl of your stand mixer. Add sugar and whip with the whisk attachment until fluffy, thick, and very light in color, 2 to 3 minutes.
• Add vanilla and 1/2 of the cocoa powder mixture; mix on low speed for a few seconds.
• Add the remaining cocoa mixture and mix on low for a few seconds. Switch to high speed and mix until the mixture is moistened but not fully blended.
• Pull off the whisk attachment and use it to whisk the batter by hand until evenly blended.
• Pour batter onto the prepared sheet pan and spread out with a spatula, almost to the edges, but not quite. Tap the pan on the counter several times to remove any large air bubbles.
• Bake in the preheated oven until the top is dry and the edges start to pull away from the sides, 8 to 10 minutes.
• While the cake is baking, sift powdered sugar onto a clean kitchen towel to cover an area slightly larger than the sponge cake.
• Remove cake from the oven. Run a knife around the edges of the pan. Dust some powdered sugar over the top. Run a spatula under the parchment paper to make sure it's not stuck to the pan.
• Quickly flip the pan on top of the sugared area on the towel to invert the cake.
• Carefully remove the parchment paper, then sift more powdered sugar over the cake.
• Gently roll the cake up inside the towel; allow to cool for 15 minutes.
• Carefully unroll the cooled cake. Dollop as much buttercream filling as you like on top, reserving some for later; spread to the edges.
• Roll cake up over the filling, using the towel to lift it if needed.
• Sprinkle more powdered sugar on top over the log, then wrap in plastic wrap. Refrigerate until firm, about 2 hours.
• Make the ganache frosting: Pour hot cream over chocolate chips in a bowl. Let sit for 1 minute, then whisk until chocolate is melted.
• Make an angled cut 3 inches from one end of the log. Place log on a parchment-lined sheet pan.
• Apply some filling to the angled slice and attach it to one side of the log.
• Spread a layer of ganache all over the cake, except for the swirls on the ends. Refrigerate for 15 minutes to firm up the ganache.
• Use the tip of a knife to carve lines into the ganache to create the appearance of tree bark. Refrigerate until completely chilled.
• Dust with cocoa powder and powdered sugar before serving.