Score the chestnuts underneath, making a slit with a sharp knife. This will make them easier to peel. Boil the chestnuts in water with the pinch of salt and the fennel seeds, for about an hour or until they are tender. Drain, and when cool enough to handle, peel, taking care to remove all of the skin.
Pass the still warm chestnuts through the fine-holed disc of a food mill into a bowl.