Torta Cioccolato e Castagne - Chocolate and Chestnut Cake

This is an alternative to pure chocolate cake. The chestnut puree softens the chocolate, giving a sweet delicate aroma. 
I mainly make it in autumn and winter, when we need more energy to face the cold. It is also a true comfort food. I like to serve it with berries and whipped cream.

Torta Cioccolato e Castagne 
Chocolate and Chestnut Cake 

200 g bitter chocolate (70% cocoa)
200 g butter
250 g chestnut puree
150 g caster sugar
4 large eggs, separated
50 g plain white flour
1 teaspoon baking powder
Butter and flour for the tin 

Icing sugar to dust
Mixed berries and whipped cream to serve (optional)

Serves 8
Preparation time: 20 minutes
Cooking time: 30 minutes

1. Grease a 22 cm spring form tin with butter and dust with flour. 
2. Melt butter and chocolate Bain Marie. Leave to cool and stir in the chestnut puree. 
3. Preheat the oven to 180°C. 
4. Beat sugar and yolks, one by one, until you get a creamy consistency. Fold in the chocolate mixture and mix. Stir in the flour and the baking powder.
5. Whisk egg whites until firm and fold into the chocolate mixture with a spatula. 
6. Arrange the mixture in the tin and bake for 25 minutes. 
7. Remove from the oven and leave to cool in the tin for 30 minutes.
8. Turn the cake out on a serving dish and serve with whipped cream and berries.