Put the potatoes to boil with the peel and leave them on the fire until the fork enters them lightly, but without breaking, then let them cool a little and peel them.
Put the potatoes on a small grater and mix them with a little salt and butter, then let them cool. When the potatoes are cold, add the egg and flour and mix well until you get a smooth and sticky dough.
Wash the plums, dry them and cut them on one side to remove the seeds, then fill them with the mixture of sugar and cinnamon and set them aside.
Put the butter in a pan to melt and put the breadcrumbs to brown a little, then put the sugar and a little cinnamon and remove from the heat.
We put a pot of water and a little salt on the fire and we start to make the dumplings.
Take the floured dough from your hand and flatten it by hand, then put a plum in the middle, cover it with the dough on the sides and round it.
When we see that the water is boiling, we put the dumplings in the pot and let them boil on the right heat until they rise to the surface, then we take them out and put them in breadcrumbs.
We serve them hot or cold.