Yule Log Cake

Filling:

1. In a large bowl, beat the butter until light and fluffy, about 1-2 minutes.
2. Add the powdered sugar, cocoa powder, salt, milk, vanilla, and mix on medium speed until well combined.
3. Increase the mixer speed to high and beat until light and fluffy. Scrape the sides and bottom of the bowl and beat in the cooled melted chocolate.
4. Using a rubber spatula, fold in the mascarpone. Cover the bowl with plastic wrap and refrigerate until ready to use.

Cake:

1. Preheat the oven to 400 degrees F.
2. Spray a 13 x 18 baking sheet with cooking spray, line it with parchment paper, spray the parchment paper with cooking spray, and set the pan aside.
3. In a small bowl, whisk together the cocoa powder, salt, and flour.
4. In a large bowl, beat the eggs and sugar until pale and fluffy.
5. Add the vanilla and half of the cocoa powder mixture, mix until combined. Add the remaining cocoa powder, and mix until combined.
6. Pour the cake batter into the prepared pan, and spread it evenly. Tap the pan lightly on the counter to remove any air bubbles.
7. Bake the cake 8-11 minutes, until a toothpick inserted in the middle comes out clean, and the edges pull away from the sides of the pan.
8. In the meantime, dust evenly a medium to large clean kitchen towel with powdered sugar, then invert the cake onto the towel, on the side with powdered sugar.
9. Remove the parchment paper and sprinkle the cake with more powdered sugar. Immediately roll the cake up into a spiral, starting from the long edge, wrapping the towel inside the cake. Let it cool for 15-20 minutes.

Add the filling:

1. After the cake has cooled, gently unroll it and spread the chilled filling in an even layer, reserving about 1/2 cup of filling.
2. Gently roll back the cake, careful not to squish out the filling. Wrap the cake in plastic wrap and refrigerate for at least 2-4 hours.

Make a log:

1. After the cake has been chilled, trim about 1/2 inch from both ends to display the nice spiral pattern.
2. After that, make a diagonal cut about 3-4 inches from one end of the cake. Then using a bit of filling, attach that piece on one side of the other piece, creating a log. Fill in any gaps with the remaining filling.

Ganache:

1. Add the heavy cream to a microwave-safe bowl and heat to boiling, about 2 minutes.
2. Place the chocolate chips in a medium bowl and pour the hot cream on top, let sit untouched for one minute, then stir until the ganache is smooth and the chocolate chips are completely melted.
3. Let the ganache cool for 10-15 minutes, until slightly thickened.
4. After that, spoon and spread the ganache over the yule log, do not cover the trimmed ends.

Refrigerate:

1. Refrigerate the cake for another 15-30 minutes, then using the back of a spoon, make a swirl pattern in the ganache to resemble tree bark.
2. Refrigerate for at least one hour, until set, before slicing and serving.