Pour the oil in a heavy frying pan and place it on the stove.

Grate the potatoes and onion onto a large clean kitchen towel. (You can also do this on the shredding blade of a food processor.)

Gather up the corners of the towel and twist the potato/onion over a large bowl. Twist tightly until liquid streams out. Keep twisting to get out as much liquid as possible. A friend can help, and you can do this in batches if it’s easier.

Heat the oil to very hot. Set a couple of layers of paper towels on a plate.

After a few minutes, gently tip the bowl to let the liquid run off. You should have a layer of potato starch at the bottom. Leave it! Add the potatoes and onion, egg, salt, and pepper. Stir very well.

When the oil is hot, scoop out a couple of tablespoons of batter into the oil and flatten slightly. You want lacy edges and a slightly thicker middle. Don’t overcrowd— the oil should keep sizzling. Cook until well-browned, about 4 minutes, then flip and finish browning.

Remove from the skillet and let drain on a towel while you make more.