Peel the potatoes and boil them or ,better, steam them. When they are ready and soft enough to be pierced effortlessly with a fork, mash them as you were making gnocchi or mashed potatoes. Choose your favourite kitchen appliance, either a potato masher or a food mill, and remove all, I mean all, the lumps. Spoon the mashed potatoes in a bowl.

Blend the almonds with the sugar until you get a powdery flour, then add them to the mashed potatoes with the melted butter, a pinch of salt and the grated zest of a lemon.

Heat oven to 180°C.

Beat for about ten minutes with an electric mixer, adding one egg at a time.

Butter a round 18 cm cake tin, dust with breadcrumbs and scrape the potato batter into the tin. Bake for about 1 hour, until the cake is dry and golden. Test the doneness with a toothpick.

Remove the cake from the oven and let it cool completely before serving, so that the lemon flavour will come out in all its freshness. A dusting of icing sugar will make the cake even more delicate.