Serves 8 – Preparation – 40 mins – Cooking Time – 10 mins
For the sponge biscuit Genoise)
- 4 Egg whites, organic or free range
- 60g Sugar, caster
- 4 Egg yolks, organic or free range
- 60g Plain flour
- 15g Butter, unsalted, melted
For the butter cream:
- 70g Sugar, caster
- 50ml Water
- 3 Egg yolks, organic or free range
- 240g Butter, unsalted, room temperature
- 30ml Dark Rum
- 200g Candied chestnuts, roughly chopped (plus a few whole ones for decoration)
For the soaking syrup:
- 40g Sugar, caster
- 40ml Water
- 25ml Dark Rum
Step 1 - For the sponge biscuit
Pre heat the oven to 180˚C.
In a food mixer on full speed, whip the egg whites while gradually adding the sugar until they reach soft peaks. Reduce the speed to medium and whisk in the egg yolks.
Remove the bowl from the machine and sieve in half the flour and with a spatula gently into the whipped egg whites. Repeat for the remaining flour trying to keep as much air as possible in the mixture.
Pour in the melted butter and mix.
Line your pastry tray with silicone paper. Place a little of the mixture under each corner of the paper to secure it to the tray and pour in the mixture.
Using a small palette knife, spread to 1cm thickness.
Cook in the pre-heated oven for 10 minutes, until a light golden colour is reached and it springs back to the touch.
Remove from the oven and leave on a wire rack to cool.
Step 2 - For the butter cream
In a small saucepan bring the sugar and water to 121˚C.
Using a whisking machine, whisk the yolks and the 30ml of water for 5 minutes on full speed until light and aerated. Turn down to a medium speed and pour the sugar syrup halfway down on the side of the bowl, making sure it is away from the whisk otherwise it will simply spray the hot sugar syrup around the bowl rather than onto the egg yolks. This hot sugar syrup will partially cook the egg yolks giving you a silky, stable sabayon.
Reduce the speed to medium and leave in the machine for 3 minutes to allow the mixture to cool to around 35˚C.
On a slow speed, add the rum then gradually add the soft, room temperature butter.
Whisk on full speed for 3 minutes to generate a little more lightness and volume. At this stage you can add the chopped chestnuts.
Reserve one third for filling the Bûche and the rest will be for decoration.
Step 3 - To build the Bûche
In a small saucepan, bring the sugar and water to the boil, then take off the heat and add the rum.
Using a pastry brush, evenly soak the sponge.
Place the sponge upside down onto a clean tea towel and peel away the greaseproof paper.
Spread one third of the butter cream over the soaked sponge, then roll the sponge into a tight roll 30cm long. Start by folding over the top edge towards you by about 1cm then use this to roll the log up, making sure that it is tight all the way through.
Wrap the log into a cylinder shape and refrigerate for 15 minutes.
Unwrap the Bûche and place it on a serving dish or cake board. Carefully trim each end to give you a straight side.
Evenly spread the remaining butter cream all over and, using a fork, mark the cream to give the impression of a log. Refrigerate for 30 minutes.
Step 4 - To serve
Dust with a little cocoa powder, Slice the end off the Bûche and place it in the middle on top so you can see the inside of the Bûche and give a sawn-off log effect.
Garnish with a few chocolate flakes by scraping your knife down the length of your chocolate bar. Add a few whole sweetened chestnuts.