Place the cubed-sized potatoes in a small pot and cover them with water.
Bring the water to a rapid boil over high heat, pot covered with a lid. Then reduce the heat to medium and cook the potatoes until they are soft or fork tender.
Drain the potatoes. Then place them back into the pot off the heat and mash them (optional), allowing all the steam to escape—reserve and allow to cool.
Place the flour in a large bowl. Add the yeast and the cooled potatoes.
Combine everything with your hands or use a stand mixer with a dough hook as an attachment. Then start vigorously kneading and add small amounts of water. The dough will be chunky and sticky at first. But keep kneading until you develop a loose ball (it'll be quick).
Then remove the dough from the bowl. Continue kneading on a well-floured flat surface and knead in the raisins, evenly distributing them. If you use a stand mixer, you simply add the raisins and let the mixer work in the dried fruits.
When you obtain a smooth and consistent dough (in about 5 minutes total), place it in a clean bowl, and cover with a clean, dry kitchen towel.
Let the dough rest and rise in a warm place or at room temperature for about 40 minutes or until the dough has increased in size by almost half.
Place the dough back on a flour-dusted work surface and shape it into a 14-inch baguette, about 2 ½ inches deep (see pics in the post).
Cut the dough crosswise into ½-inch pieces with a bread knife and shape each piece into a ball.
Preheat the deep fryer to 375°F/ 190 °C.
In batches of 3 or 4, fry the balls until golden brown (see note for air fryer).
Drain the fried doughnuts on a kitchen paper-covered plate, sufficiently spread out. Immediately sift powdered sugar over them.
Serve warm with extra powdered sugar on the side, or a ricotta cheese dip, sweetened with a drizzle of maple syrup.