Boil the potatoes.
Sift the flour, add the water, and after 1-2 minutes kneading, let it rest for 1 hour. (Autolysis: soak the flour particles.)
Add the sourdough starter and continue kneading.
In the meantime, add the boiled, mashed potatoes and at the very end the salt. Leave to rest for 45 minutes once it has thickened.
First folding is done, then rest for about 45 minutes in a greased baking dish.
After the second folding, also rest for 45 minutes.
Do the final folding and leave on the counter for 1 hour, then refrigerate for about 10-12 hours. (I prefer a slow, refrigerated rise.)
Leave to temper on the counter for 1-2 hours after refrigeration.
Divide the dough into 6 175 g dumplings, roll them on an oiled surface and cover with cellophane for about 1 hour.
Heat the oil. Shape the pancake, roll it out and put it in the hot oil. Fry for a few minutes on each side and serve.