1Preheat your oven to 180°C (350°F).
Melt the dark chocolate and butter together in a heatproof bowl over a pot of simmering water, stirring until smooth. Remove from heat and let it cool slightly.
In a large mixing bowl, beat the eggs and sugar together until light and fluffy.
Add the chestnut puree to the egg mixture and mix well.
Gradually add the melted chocolate and butter mixture to the egg mixture, stirring continuously.
Sift the whole wheat flour, chili powder, and baking powder together, then fold into the chocolate mixture.
Add the milk and mix until the batter is smooth and well combined.
Pour the batter into a greased and lined cake tin.
Bake in the preheated oven for 30-35 minutes, or until a skewer inserted into the center comes out clean.
Allow the cake to cool in the tin for 10 minutes, then transfer to a wire rack to cool completely before serving.