Chocolate Chestnut Roulade

This is in fact bûche de Noël, the French Christmas cake that represents the Yule log, burned as an encouragement to the sun to begin its ascent into the heavens after midwinter. If you're serving this at Christmas, decorate with a sprig of holly or whatever festive bits you please.

Ingredients:
Sponge
4 eggs
100g caster sugar, plus extra for dusting
100g plain flour

Filling and Covering:
225g unsweetened chestnut purée
225g caster sugar
150g dark chocolate, broken
284ml carton double cream

To finish
icing sugar for dusting

Instructions:
Preheat the oven to 190°C. Line a Swiss roll tin (about 30 x 20cm) with buttered greaseproof paper.

Whisk the eggs and sugar for the sponge until light and very thick (10 minutes or so with an electric whisk). Sieve in the flour, add 2 tbsp warm water, and fold in gently. Spread the mix into the prepared tin. Bake for 12-15 minutes, until firm to the touch.

Lay a piece of greaseproof paper on a work surface and sprinkle with caster sugar. Tip the sponge onto the paper, peel off the lining paper, and roll up the sponge, greaseproof paper and all, while still warm. Leave to cool, wrapped up.

Meanwhile, warm the chestnut purée gently over a low heat in a small pan, until warm but not hot. Stir in the sugar so the mixture turns glossy. Leave to cool completely.

Melt the chocolate in a bowl over a pan of just-boiled water. Whip the cream until thick then fold into the cool chestnut purée. Put half the mix in another bowl and fold in the chocolate.

Unroll the sponge, spread with the chestnut-only mixture, and roll up again. Spread the outside with the chestnut-chocolate mixture. Leave to set. Serve dusted with icing sugar. Serves 6-8