PUREE THE ONION, EGGS, salt, pepper and flour in a blender or food processor fitted with the steel blade, scraping down the sides of the bowl as necessary. Add the potato cubes and process until the potatoes are finely chopped, but not pureed. Scrape the mixture into a mixing bowl, and press a sheet of plastic wrap directly into the surface of the batter to prevent discoloration. Allow the batter to sit for 15 minutes. Heat the oil in a large skillet over medium high heat to a temperature of 375F. Add the potato batter in 1/3-cup pancakes, and fry until golden and firm on the underside. Turn, and fry until golden. Drain well on paper towels. Serves 6.
Note: The pancake batter can be made up to four hours in advance and kept at room temperature, with the sheet of plastic wrap pushed directly into the surface. The pancakes can be made in advance and reheated for 5 minutes in a 375F oven.