Line a large bowl with a clean kitchen towel or several layers of cheesecloth. Place grated potatoes and onion in the center of the towel, gather the corners and squeeze tightly releasing as much liquid as possible from the veggies (you want the potatoes and onions very very dry). Place veggies in a clean bowl and add egg, bread crumbs and salt. Using your hands, mix together until combined.

Heat oil in a large skillet over medium high heat. Use a 1/4 cup measure to portion latke mix into even patties. Once the oil is hot, carefully add patties to the skillet and fry until golden brown, about 2 minutes per side. Remove from the skillet and set aside on a wire rack to drain. Repeat this process, adding more olive oil if necessary.

Serve latkes sprinkled with scallions and with sour cream on the side.