Heat the oven to 200°C. Butter a 20 cm tart tin, and line with pastry. Put in a sheet of baking paper and some beans. Bake the tart shell blind for 20 minutes, remove the baking beans and cook for a further 10 minutes at 180°C.
Mix together the cream and chestnut purée, then add the eggs and egg yolk. Grate the rind and squeeze the juice of the orange and mix them in thoroughly with the cinnamon. Pour the mixture into the tart shell and bake for 40–50 minutes, until a knife stuck into the filling comes out clean.
Allow to cool and sprinkle the top with icing sugar.