Place potatoes in a clean linen towel; squeeze, reserving liquid in a measuring cup. Set aside until potato starch settles. Drain off top liquid; set potato starch aside.
In a large bowl, combine the potatoes, onion, egg, salt, pepper and reserved potato starch. Heat 2 tablespoons oil in a large skillet. Shape potato mixture by 2 tablespoonfuls into patties; place in hot oil, pressing lightly to flatten.
Fry until golden brown, about 1-1/2 minutes on each side. Drain on paper towels. Serve immediately or place in a warm oven until ready to serve.