Grind the chestnuts in a vegetable mill or blender to reduce them to small pieces.

In a thick-bottomed saucepan, make a syrup with the water and sugar. Pour the water and sugar in the pan and let it cook on medium heat.

Once the syrup has set, you can add 2 tablespoons of chestnut syrup, but this is completely optional.

Pour the chestnuts into the syrup, add the vanilla bean cut in half. Bring to the boil, then reduce the heat to low and preserve for a good 15 minutes, stirring regularly.

To thicken the cream a little, add a little milk during the cooking and mix it vigorously.

Remove from the heat, remove the vanilla bean and reserve. As you are going to use the cream directly in the cake, there is no need to mix the cream to obtain a perfectly smooth texture. The remaining small pieces of chestnuts will add crispness.

Beat the eggs in a large bowl.

Melt the chocolate and butter in a double boiler. Pour the chocolate & butter mixture on the beaten eggs and mix well.

Preheat the oven to 180°C.

Then add the flour, almond and hazelnut powder, yeast and a pinch of salt to the dough, gradually incorporating while continuing to mix.

Gradually pour in the chestnut cream and mix well. You can incorporate the rum at this stage. You should obtain a fairly liquid paste.

Pour into a cake tin covered with baking paper or buttered, and bake for 25 minutes at 180°C. Check the baking with the tip of a knife and bake for another 5 minutes if necessary.

Enjoy hot, warm or cold, plain or with whipped cream, custard or a scoop of ice cream for an even more gourmet version!