To start, prepare the filling by beating butter in a large bowl until light and fluffy. This is crucial for achieving a creamy texture. Once fluffy, add powdered sugar, cocoa powder, salt, milk, and a touch of vanilla. Mix until everything is well combined. Increase the mixer speed to high and beat until the mixture is light, fluffy, and smooth. Finally, fold in mascarpone cheese gently with a rubber spatula, then cover and refrigerate the filling until you’re ready to use it.
Next, preheat your oven to 400°F. Prepare a 13 x 18 baking sheet by spraying it with cooking spray and lining it with parchment paper. This will ensure the cake doesn’t stick. Spray the parchment with cooking spray as well, then set it aside.
In a small bowl, whisk together cocoa powder, salt, and flour. This dry mixture will help to evenly distribute the cocoa flavor throughout the cake.
In a large bowl or stand mixer, beat the eggs and sugar together until they transform into a light, fluffy, and pale mixture, which should take about 5 to 8 minutes. It’s essential to achieve this texture as it contributes to the cake’s lightness.
Once the egg mixture is ready, gently add in vanilla and half of the cocoa powder mixture, mixing until just combined. Then, fold in the remaining cocoa powder mixture, ensuring not to overmix to retain the airiness.
Now, pour the cake batter into the prepared pan, spreading it evenly. Gently tap the pan on the counter to eliminate large air bubbles. Bake the cake for 8 to 10 minutes, or until a toothpick inserted in the center comes out clean and the edges pull away from the sides.
While the cake is baking, dust a clean kitchen towel with powdered sugar. When the cake is done, carefully invert it onto the towel, remove the parchment paper, and sprinkle more powdered sugar on top. Roll the cake up into a spiral, starting from one long edge, wrapping the towel inside. Allow it to cool for 15 to 20 minutes.
Once the cake has cooled, gently unroll it. Spread the filling evenly across the cake, saving about half a cup for later. Carefully roll the cake back up, ensuring not to roll too tightly, so the filling doesn’t squish out. Wrap the rolled cake in plastic wrap and refrigerate for at least two hours to firm up.
After chilling, trim both ends of the log to reveal the spiral pattern. Make a diagonal cut about 3 inches from one end of the cake and attach this cut piece on one side with the remaining filling, filling in any gaps.
Now let’s make the ganache. Heat the heavy cream in a microwave-safe bowl until it reaches a boiling point, which should take about 2 minutes. Pour the heated cream over the semi-sweet chocolate chips in a separate bowl and let it sit for a minute. Stir until the ganache is smooth and the chocolate is fully melted.
Allow the ganache to cool for 10 to 15 minutes until it slightly thickens. Then, spoon it over the Yule Log, ensuring to cover every surface except for the cut ends. Refrigerate for an additional 15 minutes, then create a swirl pattern in the ganache to mimic tree bark using the back of a spoon. Lastly, refrigerate for at least one hour until set.
When ready to serve, transfer the Yule Log to a serving platter and sprinkle with a final dusting of powdered sugar for that snowy finish.