Chocolate and Chestnut Cake

By corlear

Gâteau Lyonnais
Olivier de Serres, often called the father of French agriculture, wrote in 1599 of the chestnuts of Lyon, "which is known throughout France for its trade in this fruit." If using fresh chestnuts instead of canned chestnut purée for this recipe, peel the chestnuts and simmer them until soft in a mixture of milk and water. Then drain and purée in a food processor or blender.

Ingredients

• For the cake:
• 90 g (3 oz) semi-sweet chocolate, chopped
• 4 eggs, separated
• 200 g (1 cup) sugar
• 200 g (7 oz) canned unsweetened chestnut purée
• 20-23 cm / 8-9 in springform pan or round cake pan
• For the frosting:
• l50 g (5 oz) semi-sweet chocolate, chopped
• 2 Tbsp water
• 2 egg yolks
• 125 ml (1/2 cup) heavy cream
• 1 Tbsp sugar
• 1/2 Tbsp rum, or to taste

Details

Servings 8

Preparation

Step 1

Butter the pan and line the bottom with a buttered round of greaseproof/parchment paper. Set the oven at moderate (175°C/350°F).

Make the cake:
Melt the chocolate in a small bowl over a pan of hot water and set aside until cool but not set.

Beat the egg yolks with three-quarters of the sugar and the chestnut purée until thick and light.

Whip the egg whites until stiff, add the remaining sugar and continue to whip for another 30 seconds or until glossy.

Stir the chocolate into the chestnut mixture, then fold in a quarter of the egg whites. Add this mixture to the rest of the whites and fold them together gently. Pour the mixture into the lined pan. Bake in the heated oven for 30—35 minutes or until a skewer inserted in the cake comes out dry.

Let the cake cool in the pan; then carefully unmould it and set aside on a rack.

Make the frosting:
Melt the chocolate with the water in a small pan set in a water bath; whisk until smooth. Remove from the heat and beat the yolks one at a time into the hot mixture.

Return the pan to the water bath and whisk for 1—2 minutes until slightly thickened. Remove from the water bath and set aside until cool but not set.

Whip the cream until it holds a shape; then fold it into the cooled chocolate mixture (if warm it will melt the cream). Add the sugar and rum to taste.

Spread the frosting on the top and sides of the cake and transfer it to a platter.