Place the milk in a saucepan, add the creme de marron and bring to the boil.
Break the eggs in to a bowl. Add the sugar and beat until pale and fluffy. Add the flour and mix well to get rid of any lumps.
Pour the hot milk over the eggs/sugar/flour and mix well. Return to the pan and cook over a low heat to thicken the cream. Once the base of the pan is visible as you mix, the cream is cooked. Remove from the heat and chill for 1 hour.
Use an electric whisk to beat 200ml of cream until it is thick and will form peaks. Check that the crème pâtissière is cold then mix the two creams together. Fill a piping bag with the mixture.
Place the sugar in a hot frying pan and melt without stirring. Once you have a caramel, add the salted butter and 200ml cream. Bring to the boil and cook for 2 minutes.
Fill the choux pastry buns with the chestnut pastry cream, coat with caramel and serve.
«Try replacing the creme de marron with pistachio or hazelnut cream for another delicious dessert.»