Instructions: First deal with tbe fresh chestnuts.

Score an X in the skin and put them into a pan with enough waler to cover.

Bring up to the boil and simmer for a minute.

Draw if the heat but not drain.

Take chestnuts out and peel one or two at a time bringing the water back to the boil when necessary.

Put the peeled chestnuts into a pan with the vanilla pod and pour in ono milk to cover.

Bring up to the boil and then simmer until the chestnuts are very tender Drain and pick out the vanilla pod.

Put the chestnuts into the processor with the chocolate and whizz until very very finely chopped scraping down the sides frequently.

Beat the egg yolks with the sugar until light and pale.

Fold in the chestnut and chocolate mixture.

Mix the egg whites until they form stiff peaks and fold in.

Divide the mixture between two 20cm cake tins lined with non stick baking parchment spreading it down lightly.

Bake for about 20 minutes at 180C/350F/Gas Mark 4 until just firm.

Cool for 20 minutes in the tin then turn out and finish cooling on the baking parchment on a cake rack (the cakes are too delicate to be placed on it directly).

To make the filling break the chocolate into pieces and place in a bowl set over a pan of gently simmering water making sure that the base of the bowl does not touch the water.

As soon as the chocolate has melted lift the bowl off the pan and let the chocolate cool until barely tepid.

Whip the cream and fold into the chocolate.

Spread the mixture over one of the cakes scatter with chopped marrons and sandwich with the second cake having carefully peeled off the parchment.

To make the icing melt the chocolate as before then gradually beat in the butter a little at a time.

Cool until begining to thicken then spoon over the top and down the sides Decorate with marrons glaces (if using) before the icing sets.

Serves 10

Any problems are readily disguised with strategic blobs of filling or icing as appropriate. The finished cake will keep in the fridge for several days so can be made ahead of time.

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