Melt the dark chocolate and cream together. Place in the fridge to cool completely. I like to make the sponge while its cooling.
Once cold, place the ganache in a bowl and, using a hand beater, beat the ganache until it begins folding over one another and you have a soft whipped cream or mousse. Do not beat until stiff as the cream will curdle!
Place in the fridge until needed.
Chocolate Buttercream;
I like to make the buttercream either the day before or while the sponge is cooling.
Place the cream cheese, butter and melted chocolate in a bowl and with a stand mixer or hand mixer, beat until all combined. Add in the cocoa and icing sugar slowly with the beaters on low so it incorporates slowly without flicking around.
If the mixture is too stiff, add a touch of water to the mixture until you have a spreadable consistency.
Set aside until needed.
Chocolate Sponge;
Preheat the oven to 180°C (350F) and line a 13"x9" baking pan with baking paper and set aside.
Separate the eggs and place the egg whites into the bowl of a stand mixer. Whisk on high speed for about 2 to 3 minutes until soft peaks form. You want soft peaks (the tips curl) not stiff peaks like a meringue.
In a separate large bowl, whisk the egg yolks and sugar together until they're pale yellow. Add in the cocoa, flour, coffee granules, baking powder, and salt and whisk to combine. The batter will be stiff and sticky.
Add in a third of the egg whites and, using a spatula, mix this into the egg yolk batter to loosen it and get all the batter unstuck from your bowl. Add the next third of egg whites and fold those through being more gentle with the egg whites so you don't knock out the air bubbles.half of the egg whites and use a rubber spatula to gently fold the whites into the batter.
Repeat with the remaining third of egg whites.
Pour the sponge into the prepared pan and even it out into all the corners. Bang the pan on the bench twice and then place it in the oven for 10 minutes. Its important not to overcook the sponge so when a skewer inserted in the middle comes out clean or with one or two loose crumbs, take it out of the oven and let it set for two minutes.
While the cake is sitting, take a clean tea towel or sheet of baking paper and dust with cocoa powder.
Flip the cake out onto the towel and very gently peel the baking paper off inch by inch. Grab one of the short sides of the cake and roll it towards the other short side, rolling the towel or baking paper with it as you go. Let the cake remain in this rolled shape until it's completely cool. (Note: It’s important to do this while the cake is still warm as the cake is still flexible at this point and this prevents the cake from cracking or tearing as you roll it).
Let the cake remain in this rolled shape until it's completely cool. (I place mine in the fridge to speed up the cooling process).
Once cooled, unroll your sponge gently and spread the chocolate mousse in an even layer over the sponge leaving a small border around the edges.
Reroll your sponge (this time without the towel or baking paper) and set it on your serving plate, seam side down.
Slice around a 2" slice off one end on an angle. So one end will be around 2" and the other end will be around 1". Sit this angled piece onto the side of the cake.
Take your butter cream and do a thin layer of the buttercream over the full yule log. This is your crumb coat. I like to have a glass of warm water handy to dip my knife in and make the spreading process easier.
Top with the remaining buttercream and smooth it all over the yule log.
Take a fork and run it down the cake to create "bark' indents and dust with a sprinkle of icing sugar for the snow.