Using box grater or in food processor using the larger shredder blade, alternately shred the potatoes, sweet potatoes and the onions. (Alternating the potatoes with the onions helps keep the potatoes from browning!!). Transfer mixture to colander. With hands, squeeze out as much of the moisture as possible – this will help keep the latkes crispy). Transfer squeezed mixture to large bowl.

Mix in eggs, flour, salt and pepper. Let stand for five minutes. Pour off any excess liquid.

In large skillet, heat a qurater inch of oil over medium-high heat until oil is very hot but not smoking. Using a quarter cup measure or ladle, add latke mixture to skillet, leaving about one inch between them. Flatten slightly. Fry for about three minutes, or until well browned and crisp around the edges. Flip over; fry for another three minutes, or until crisp and golden brown. With slotted spoon, remove to paper towel-lined baking rack.

Repeat with remaining mixture, removing any bits from skillet that are too blackened and adding oil as necessary.