Grate potatoes and onions. The onions not only make the pancakes delicious and lush, but also prevent the potatoes from darkening.
Add eggs, flour, salt and pepper and mix well. The potato and onion juice might seep out into the bowl, so periodically tilt the bowl to pour it out.
Place tablespoon-sized dollops of potato mixture into a well oiled, preheated pan. Press down on each derun lightly with a spatula, and fry on medium heat on each side until golden brown, about 3-4 minutes per side.
Serve with sour cream