
Serves 8-10
1. Preheat the oven to 170°c/Gas Mark 3 and grease and line a 23cm-diameter springform cake tin.
2. Melt the chocolate and butter together in a pan over a very gentle heat. In another pan, heat the chestnuts with the milk until just boiling, then mash thoroughly with a potato masher (or process to a rough purée in a machine).
3. Put the egg yolks in a bowl and mix with the caster sugar. Stir in the chocolate mixture and the chestnut purée until you have a smooth, blended batter. Whisk the egg whites until stiff and fold them carefully into the batter.

4. Transfer the mixture to the greased, lined tin and bake for 25–30 minutes, or until the cake is just set but still has a slight wobble.
5. If you want to serve the cake warm, leave to cool a little, then release the tin and slice carefully – it will be very soft and moussey. Or leave to go cold, when it will have set firm. Its good to serve it with a trickle of double cream, especially when warm, but it is also delicious unadulterated.
© River Cottage