Grate the potatoes and onion using the small holes of a box grater or a food processor.

Transfer the grated mixture to a large bowl and let it sit for a few minutes. Drain any excess liquid by pressing the mixture against the side of the bowl with a spoon or hands.

Add the egg, flour, salt, and pepper (if not using sugar). Stir well until combined. If the batter feels too wet, add a bit more flour.

In a large skillet, heat plenty of oil over medium heat until hot enough for the batter to sizzle.

For each pancake, spoon about 1/4 cup of the batter into the skillet. Flatten slightly to make a pancake about 1/4 inch thick.

Cook until edges are crispy and golden brown, about 3-4 minutes on each side.

Transfer cooked pancakes to a plate lined with paper towels to remove excess oil.

Serve hot, either with a sprinkle of salt or with sugar and a dollop of sour cream.