In a food processor fitted with the shredding disk, shred potatoes and onions, using medium pressure. Transfer vegetables to a large colander set in the sink or over a bowl; press firmly to drain excess liquid.

Place drained veggies into a large bowl. Add eggs, potato starch, baking powder, salt, and pepper. Mix well.

Place chicken into potato mixture; coat on all sides.

In a large nonstick skillet, heat oil over medium-high heat. Working in batches, fry chicken on both sides until cooked through and juices run clear, three to five minutes per side.

Pat chicken with paper towel to remove excess oil.