Combine the egg, flour, potato starch, salt and pepper, and onions in a mixing bowl. Stir until smooth. This effectively beats the egg, and combines all the ingredients so mixing them through the shredded potatoes is more predictable.
Grate the potatoes right onto a napkin, square of cheesecloth, or super-strong paper towel.
Squeeze the potatoes in the cloth or paper towel to extract as much moisture as possible.
Add them to the bowl with the egg mixture, and stir it through thoroughly.
Divide the mixture into four piles.
Heat ¼ cup of oil in a heavy skillet with at least a 10-inch diameter base. Use medium-high
Add the potatoes to the hot pan and immediately flatten them to your desired thickness, using the back of a spoon.
Cook until well browned on the first side. Adjust the heat if required to prevent them browning too quickly. Flip carefully, perhaps using a flipper and a fork, to minimize the potential to splash oil during the process.
Cook on the second side until equally nicely browned. Remove to a paper towel to drain, and immediately sprinkle with a little salt.