Peel potatoes, cut into small pieces and submerge them in a bowl of cold water to prevent discoloring. Peel onion and cut into pieces. Coarsely grate potatoes and onion using the grater attachment of the food processor. (Alternatively, if you do not have a food processor, you can grate the whole potatoes and onion on the large holes of a box grater.) Transfer to a large mixing bowl. Add eggs or 2 tablespoons olive oil, flour and salt and stir to blend.
Line two cookie sheets with aluminum foil or parchment paper. Top each with a double thickness of paper towels.
Coat the bottom of a large skillet with olive oil (1 to 2 tablespoons) and heat to medium high. Drop about 2 tablespoons potato mixture onto hot oil. Press gently to flatten and fry for several minutes or until underside is golden. Flip and brown the other side.
Drain pancakes on cookie sheets while frying the next batch. Blot with paper towels and transfer to platter. Keep latkes warm until ready to eat.