Make potatoes, peel, mash and cool. In a saucepan, steam the plums for about 20 minutes until soft, pour off the water and cool. Remove the seeds from the plums, cut them into small pieces, mix them in a baking bowl with the juice of one lemon, the zest, the walnuts and sugar.
Knead the potatoes with the lard, egg yolks, flour and salt into a dough. Roll out into 7 mm thick rectangles and cut into 8 cm squares. On the squares form 1 tsp of the filling, wrap corners and form into dumplings. Poach the dumplings in salted water for about
25 minutes. Roll drained dumplings in a mixture of cinnamon, bread crumbs and sugar.
Bring to the table hot.