Chocolate ganache:

1. Add the chocolate and heavy cream to a microwave safe bowl. Microwave in 20 second increments, stirring in between, until the chocolate fully melts and a smooth ganache forms
2. Let the ganache cool down fully at room temperature until it reaches a thick, spreadable consistency. This can take 60-90 minutes. During this time, you can work on the rest of the cake (see notes if you want to chill it faster)

Chocolate genoise cake:

1. Pre-heat oven to 350F (conventional / no fan) and prepare a 10x15" baking sheet by placing parchment paper on the bottom. Do not add oil or butter
2. Add the eggs and sugar to the bowl of your stand mixer and use the whisk attachment to whisk on medium high speed for 5-7 minutes until the mixture becomes very pale in color, thick and fluffy in texture, and almost triples in volume. Do not rush this step!
3. Now sift in the flour, cocoa powder, baking powder and salt
4. Use a rubber spatula to very carefully, gently and slowly fold the dry ingredients into the wet. Take your time and do not use an aggressive mixing motion because you don't want the air to be knocked out of the batter. Stop folding as soon as no more streaks of flour can be seen. You should have a very fluffy batter
5. Carefully transfer the batter to the prepared baking sheet and spread it out evenly
6. Bake in the pre-heated oven for ~10 minutes or until a toothpick inserted in the middle comes out clean. Do not over bake!
7. While the cake is still baking, lay out a tea towel on your counter (should be bigger than the cake) and dust it with icing sugar all over
8. When the cake is done baking, remove it from the oven and use a spatula / butter knife to carefully release the edges from the pan. Carefully flip the cake onto the tea towel while it is still hot, and peel off the parchment paper and dust more icing sugar on top of the cake
9. Keep the short end of the cake facing you. Holding both the cake and the tea towel, slowly roll up the cake along its length as tightly as you can without applying pressure (meaning your roll at the end should be 10" long, not 15" long)  
10. Place the rolled up cake in the fridge until it fully cools down (about 30 minutes)

Cherries and syrup:

1. Drain the canned cherries and reserve the liquid. Save a handful for decoration, and roughly chop the rest
2. Place the liquid in a saucepan and cook on low heat for 5 minutes to reduce it slightly. Set the syrup aside

Chantilly whipped cream:

1. Add the cold heavy cream, sugar, salt and vanilla to a bowl. Whisk on medium high speed for a few minutes until the cream reaches a medium stiff peak consistency. This means the cream should be able to hold shape but not be too firm or grainy

Assembly:

1. Once the cake has cooled down, remove it from the fridge and carefully unroll it
2. Use a pastry brush to brush a generous amount of the cherry syrup all over the cake. You can it well coated, but not soaking because that can cause the cake to break
3. Spread a generous layer of the chantilly whipped cream on the cake as evenly as possible. You should use up at least 3/4 of the cream, reserving the rest for decoration
4. Spread the chopped cherries all over and gently press them into the cream
5. Now carefully and slowly roll the cake in the same direction again, this time with the fillings and without the tea towel. Try to do this as tightly and neatly as you can without causing the filling to ooze out or the cake to break. It is totally fine if some filling oozes out
6. At this point, you can wrap the cake in cling wrap and place it in the fridge again. If you're ready to decorate, you can move to the next step
7. Carefully transfer the cake to a serving stand. Apply a generous coating of the ganache all over (you can cover up the sides too, but I like to keep them exposed so the swirl is visible). Use a fork to form ridges in the ganache to give the look of a tree bark 
8. Transfer the remaining cream to a piping bag with a star tip, and pipe swirls on top of the cake. Top each swirl with a cherry, and garnish with chocolate shavings / powdered sugar
9. Keep cool, serve and enjoy!