Gluten Free Bûche de Noel

Instructions

1. Make the sponge cake: First preheat the oven to 180°C and line the baking pan (roughly 35 cm long and 28 cm wide) with parchment paper, then lightly grease the paper with coconut oil. 
2. In the bowl, mix together hazelnut meal with walnut meal, potato starch, baking powder and cocoa powder.
3. Using a hand mixer or a stand mixer whisk the egg whites over high speed until light and foamy. Gradually add coconut sugar, whisking on high speed. Then lower the speed and add egg yolks, one by one, mix until combined.
4. Slowly add the flours and mix in gently with the whisk or spatula until smooth and fluffy. Transfer the batter onto the prepared sheet pan and spread into an even layer using an offset spatula (the batter should fill the entire pan).
5. Bake for 10 to 12 minutes. In the meantime lay a clean kitchen towel on a flat surface and dust with coconut sugar. Once the baking is done gently invert baked cake onto a prepared kitchen towel, peel off the baking paper. Slowly roll the cake with a kitchen towel, rolling from the short end to the other short end. Let the cake cool completely.
6. Prepare chocolate shard: Melt 200 g chocolate over bain-marie. Cut a few pieces of parchment paper ( A5 size). Then spread chocolate evenly on parchment paper pieces into a thin layer. Roll each paper and place into plastic cups or other round things, which will help to keep the shape rolled. Refrigerate for 30 minutes. Unroll the parchment paper and break the chocolate into shards. Make them as big as desired. Place ready shards back in the refrigerator. Try to avoid touching the pieces with your hand as the warmth will melt the chocolate.
7. Make chocolate cake filling: Using an electric mixer whisk together mascarpone cheese, cocoa powder, instant coffee powder, xylitol and vanilla extract. Then slowly add the whipping cream and keep whipping until the mixture is smooth and firm. Don’t overwhip as that might cause the cream to have a grainy texture or eventually turn into butter. 
8. Gently unroll the cooled cake, and spread the filling into an even layer onto the top. Then carefully re-roll the cake, without the towel this time. Place the cake in the refrigerator and make the chocolate ganache.
9. Chocolate ganache: Mix chopped chocolate with heavy whipped cream in a bowl and warm up over a bain-marie. Stir it until melted and well combine. 
10. Pour ganache all over the cake roll. Feel free to spoon up over the cake any dripped ganache. 
11. Immediately decorate the cake roll with chocolate shards before the ganache gets solid. Place the cake in the refrigerator for at least 2 hours. Use a hot knife to slice the cake.