Neapolitan Potato Doughnuts

Method

1. Boil whole potatoes until tender, then mash them.
2. In a stand mixer bowl, combine the flours, sugar, mashed potato, lightly beaten eggs and yolk, vanilla bean seeds, crumbled yeast, and orange and lemon zest. Knead for a few minutes until the dough comes together.
3. After a few minutes, add salt and incorporate.
4. Gradually add the soft butter, a little at a time, allowing it to absorb completely. Continue until the dough is smooth, silky, and elastic.
5. Transfer the dough to a work surface, give it a few folds, then shape it into a ball.
6. Place the dough in a container, cover with plastic wrap or a cloth, and let it rise until doubled in size.
7. Dust the surface with flour and roll out the dough with a rolling pin to a thickness slightly over 0.5 cm (about 1/4 inch).
8. Using a ring cutter, shape the dough into donuts with a hole in the center.
9. Place the donuts on a lightly floured kitchen towel, cover them, and let them rise again until puffy.
10. Heat sunflower oil to 160–165°C (320–330°F). Fry the donuts slowly until golden brown on both sides. Monitor the temperature.
11. Drain the donuts and immediately toss them in a mixture of sugar and ground cinnamon.