To prepare the potato donuts, wash the potatoes and place them in a large pot, covered with plenty of cold salted water. Place on medium heat and, once boiling, let cook for about 30-40 minutes, depending on the size of the potatoes. To check for doneness, pierce them with a fork: if the tines go in easily to the center, you can drain them.

In a bowl, sift the flour, make a small well in the center and pour in the brewer’s yeast dissolved in two fingers of warm water, the two beaten eggs, the sugar, the extra virgin olive oil, a pinch of salt, the vanillin, the grated lemon zest, and the peeled and mashed potatoes with the help of a potato masher.

Knead everything together until you get a smooth and homogeneous mixture. If the dough is too sticky, add a little flour at a time until the right consistency is reached. Cover the bowl with plastic wrap and let it rise for 4-5 hours or until doubled.

After the rising time, take a portion of the dough and work it with your hands to form long ropes about 0.6 inches thick. Cut each rope into pieces of about 4 inches, then close them forming the classic donut shape.

Place a pan on the heat with plenty of seed oil (or olive oil) and bring to a temperature of 356°F. Dip the donuts and cook until golden brown, remove them with a slotted spoon and transfer them to a dish lined with kitchen paper to absorb the excess oil.

Once all the donuts are cooked, in a bowl, pour the granulated sugar and cinnamon, to taste. Dip the donuts to coat them well with the sugar and cinnamon, then arrange them on a tray.

Your potato donuts are ready to be served.