This recipe is Martha Stewart’s Chocolate Genoise with a few notes added to it. I used a sieve for all the sifting.
Recipes will tell you not to over bake the cake because it will crack. Cracking can happen when you don’t over bake the cake, like if you put the cake in the refrigerator and unroll it when it’s cold. But the filling and icing will fix them. What you don’t want is for your cake to be dry or tough.
All the steps are important but the two critical steps are how long you beat the egg mixture, and how long you bake the cake. I found Chef John’s Chocolate Yule Log video very helpful. Chef John will show you exactly what the egg mixture looks like when it’s been beaten for the correct length of time. And he shows you the tapping of the cake pan to release the bubbles before baking. I recommend watching his video before beginning this recipe.
Chocolate and Hazelnut Buche de Noel
Start with mise en place: Make the genoise (recipe below). Make the chocolate hazelnut spread (get blanched hazelnuts to make it MUCH easier), and the chocolate mousse and chocolate ganache icing and the meringue mushrooms.
Blend the 2 cups of chocolate hazelnut spread and the 1/3 cup Frangelico in a food processor until smooth.
Follow Martha Stewart’s assembly instructions but when you get to the filling, spread the chocolate hazelnut mixture over the cake and then the chocolate mousse.
For everything I used half Ghirardelli semi-sweet and half bittersweet chocolate pieces (found at Target and Walmart) mixed together.
You can use plain rosemary and cranberries or for sugared rosemary and cranberries see How to Make Sugared Cranberries and Rosemary. Wilton’s White Sprinkling Sugar works well for the sugar you sprinkle on the berries and rosemary after the simple syrup has dried for an hour.
Martha Stewart’s Chocolate Genoise
Preheat oven to 350 degrees.
Prepare an approximately 12″ by 18″ jelly roll pan (baking sheet with straight 1″ sides) by buttering the bottom, cutting out a piece of parchment to fit the bottom and laying it down and buttering and flouring the parchment, tapping out the excess flour.
Take out two small bowls. Set a sieve over one of the bowls and add the flour, cocoa and baking soda and sieve them into the bowl. Then place the sieve over the other bowl and dump the ingredients into the sieve again and tap the sieve until the mixture is in the bowl. Set aside.
Melt the butter in a small pot and keep warm.
Put the eggs and sugar in your mixer bowl. Set the bowl over a pot with steaming water. Gently mix the eggs and sugar with a whisk until the mixture just barely is starting to warm and the sugar has dissolved (test it ofter with your finger), then place the bowl in your mixer and beat on high for 7 minutes. It will triple in volume. At this point it should form a ribbon as you lift the beater that falls back onto the surface then partially disappears back into the mixture, rather than stiff and holding its shape. Stop and check until it’s right. (See Chef John’s video starting at the 2:50 and he will show you exactly what this looks like.) When you are at this place, change the mixer speed to medium and add the vanilla. Then remove the bowl from the mixer.
Sift 1/3 of the flour and cocoa mixture over the egg mixture and fold it in with a rubber spatula. Repeat 2 more times. Drizzle the warm butter over the mixture, leaving behind the milk solids at the bottom of the small pot. Fold the butter in. Gently pour the cake batter into the prepared pan. Spread it evenly to the sides and into all the corners and smooth the top. Lift the pan and drop it gently two times to release bubbles in the batter. Bake the cake in a 350 degree oven for 13 to 17 minutes, depending on the size of your pan (a 12″ by 18″ takes 13 minutes and a 10″ by 15″ takes longer). It will have pulled away from the sides and you should be able to gently press the center with your finger and it won’t leave a dent.
While warm run a knife around the edge of the cake to release the sides, dust the top of the cake with cocoa using a sieve and lay a piece of waxed paper over it. Then tip it over onto the damp dish cloth. Remove the parchment and dust the bottom of the cake with cocoa. Roll the cake up in the dish cloth and let it cool completely. I recommend filling the cake the day you make it as refrigerating it can make it much more difficult to handle.
The 2 Layer Filling – Chocolate Hazelnut Spread With Frangelico and Chocolate Mousse
Layers 1 and 2
The Icing and Decorations
Heating the cream is like scalding milk which will rise and spill over the pan it you aren’t watching it. After the skin has formed and the cream just starts to rise, pull it off the heat.
At first it will be very light. Keep stirring and it will become darker. Then you have two options. Ganache becomes thicker as it cools. Putting it in the refrigerator speeds up the process. The easier option is to let it get just cold and then beat it until it’s a frosting consistency which is lighter in color. Or you can keep it in the refrigerator and come back and check on it, stirring it until it becomes a fudge-like spread, darker in color, without any whipping. I prefer the icing version for this cake.
I left out the tablespoon of cocoa that was called for that is added to the meringue and just did the sprinkling of cocoa on top. Baking them for 2 hours according to Martha Stewart’s directions turned them the off white color so they looked like woodsy mushrooms. After attaching the stems and laying them in the egg carton, I put them briefly in the refrigerator to harden the chocolate. Don’t add them until the last hours before serving. They become mushy next to the cake in the refrigerator.