Preheat oven to 350°F. Line your 10 x 12 pan with a parchment paper and generously spray with non stick oil
Move your oven rack to the middle and pre heat oven at 350 F.
Separate egg whites from the egg yolks. Put the egg whites in the stand up mixer bowl, and the yolks in the medium sized bowl. SET ASIDE.
MAKE THE YULE LOG FILLING:
In a stand up mixer bowl, add whipping cream and Mascarpone cheese and sugar. Mix all of the ingredients on medium high speed and mix until stiff peaks. Set aside and refrigerate until you are ready to fill.
PREPARE THE CHOCOLATE CAKE:
In a small bowl, mix the baking powder, salt and cocoa powder. Mix using wire whisk and Set aside
In a bowl, with the egg yolks. Using hand or stand mixer, whisk the yolk with the sugar. Add the softened butter until pale in color and add the rest of the ingredients. Add the flour ingredients and gently mix until there's no lumps.
Attach bowl containing the egg whites and mix on medium high speed until stiff peaks. Add half of the egg whites to the egg yolk mixture and gently fold mixture until there is no white streaks. Add the rest of the remaining egg whites into the egg yolks and gently fold mixture. When ready, pour in batter mixture into the prepared baking sheet and bake for 13 to 20 minutes. Start checking cake using toothpick method starting in 13 minutes. When the toothpick comes out clean, then take it out from the oven.
While the cake is still hot,scrape the sticking side of the cake off using a knife. Sprinkle the top of the cake with powdered sugar and cover with a towel. With one end of the towel extending about 2- 3 inches out of the cake. Put a cooling tray on top and flip the cake.
Very gently roll the cake and let it cool.
When the cake is cool, unfold the cake and fill the whole cake with the filling leaving 2- 3 inches on one end unfilled. Very gently roll the cake tightly and the wrap with wrapping plastic and refrigerate until ready to fill.
TO MAKE THE GANACHE:
While the cake is cooling, out the chocolate morsel in a medium sized bowl. Warm the whipping cream for 10 minutes and pour into the chocolate morsels. Using a spatula, mix them together and let the morsels melt. Let it cool.
WHEN CAKE IS COLD AND READY :
Place cake in a flat serving tray and decorate the cake, use a large serrated knife to gently cut off a piece of the log about 3 inches in length. Make the cut with a slight diagonal.
Use some of the chocolate ganache to attach the small log to the side of the larger log. Spread the remaining chocolate ganache all over the cake, then use a fork to create bark-like lines all over it. Decorate with sugared cranberries and rosemary (instructions in notes), if desired.
Refrigerate the cake until ready to serve.
If you have left over ganache, put it in a sealed container and freeze.