Bûche de Noël is traditionally made in France for Christmas. When I managed a French artisan bakery it was Christophe's specialty and he used to make three flavours, chocolate, coffee and a white chocolate and raspberry. Hotels and restaurants loved to order them for a centre piece.
I have to be honest and admit I had never made one until now but I used to watch Christophe making them.
Chocolate Bûche de Noël
The first thing to make is the crème au beurre or buttercream.
Crème au beurre
125g unsalted butter
1 egg and 1 egg yolk (reserve the white)
1 tablespoon cocoa powder
1 teaspoon of rum
Soften and whisk the butter in one bowl. In another bowl whisk the eggs and stand aside.
Measure out the sugar and water accurately and place in a small pan with a sugar thermometer. Dissolve the sugar and then heat until you reach 121 degrees C. If you are using a heavy based Le Creuset pan for example remove from heat when you hit 120 degrees as the temperature will continue to rise. Cool to 110 degrees. Continue to whisk the eggs adding the cooled sugar syrup in a steady stream. Continue whisking for another few minutes. Add this mixture to your whipped butter. Add in cocoa powder and rum and place in fridge to stiffen up.
For the sponge
4 eggs and the reserved egg white
1 tablespoon cocoa powder
Line a swiss roll tin with baking parchment and grease it with a knob of melted butter. Mine was 36 x 25cm or 14 x 10 inches but you can use a bigger one to get a thinner sponge which makes rolling it easier.
Pre-heat your oven to 170 deg C or 160 if fan assisted.
Put the eggs and sugar in a bowl and place over a saucepan of water. Put the heat on under the pan and bring to a gentle simmer all the time whisking the eggs and sugar. When it turns thick and creamy and you can write on the mixture with your whisk and it remains visible for a few seconds it is done.
Sieve in your flour and cocoa powder and gently fold in with a metal spoon. Pour the mixture into the tin and tilt the tin to move the mixture into the corners.
Place on the bottom shelf in the oven and bake until it springs back to a gentle touch for 25-35 minutes. Place a damp tea towel on a board and slide the sponge out of the tin onto it. Cover with a dry tea towel and leave to cool.
When it is cool spread the buttercream gently all over it with a pallet knife or a spatula. Cut a line about 1cm in along the shorter side and fold this over and start to roll from here using the greaseproof paper to guide it into a tight roll.
Set aside and prepare your ganache to cover the log.
250g dark chocolate or half and half dark and milk if you don't like it too bitter
Break up the chocolate pieces into the cream in a heavy based pan and put on a gentle heat until the chocolate starts to melt. Stir until it all melts and then set aside to cool. When it is the right consistency to spread cover the sponge and make marks in it to resemble a log. Decorate and serve.
For the coffee flavour replace the cocoa powder with 2 teaspoons of coffee liquid extract. For the white chocolate add 75g of melted white chocolate to the buttercream and make a white chocolate ganache as above to cover.