Line a colander with a clean kitchen towel or several layers of cheesecloth and set it over a bowl. Coarsely grate the potatoes and onion using a box grater or food processor shredding disk. Transfer the mixture to the lined colander.
Gather the towel around the potato mixture and squeeze firmly over the bowl to remove as much liquid as possible. Discard the liquid, but keep the white potato starch that settles in the bottom of the bowl. Add the squeezed potato mixture back to the bowl with the starch.
Stir in the eggs, flour, salt, pepper, and optional nutmeg until evenly combined. The mixture should be moist and hold together when pressed in a spoon. If it seems very loose, stir in 1 additional tablespoon flour (8 g).
Heat about 1/4 inch (6 mm) of oil in a large skillet over medium to medium-high heat. When a small strand of potato sizzles steadily, add about 1/4 cup (60 ml) potato mixture per pancake. Flatten each mound into a 3- to 4-inch (8- to 10-cm) round.
Fry in batches without crowding the skillet until deep golden and crisp on both sides, turning once with a thin spatula. Adjust the heat as needed so the pancakes brown steadily without becoming too dark before the potatoes cook through.
Transfer the cooked pancakes to a wire rack or paper towel-lined plate. Add more oil between batches if the skillet looks dry. Serve hot with applesauce, or choose sour cream and chives for a savory version.