Preheat oven to 350 degrees F. Place 10-inch cast iron pan in oven while preheating.

Use food processor or grater to grate potatoes into long strands. In large mixing bowl, place potatoes and fill bowl with cold water.

Use food processor or grater to grate onion, reserving juice and pulp.

Using mesh strainer, strain shredded potatoes and rinse with cold water. Press down on potatoes to squeeze out as much water as possible and place back into bowl. (Note: Add potatoes to clean cotton kitchen towel and wrap and squeeze to really get out all water.)

Into bowl with potatoes, pour in grated onion with juice and pulp and toss until combined. Sprinkle potato starch over mixture and toss well. (Note: There should be no lumps of starch.)

In medium bowl, mix together eggs, kosher salt, black pepper and 2 tablespoons oil. Pour egg mixture over potato and onion mixture, toss to combine well.

Carefully remove cast iron pan from oven and add 1 tablespoon oil.

Pour potato mixture into pan and evenly distribute. Drizzle on remaining 2 tablespoons oil.

Bake 70–75 minutes, until browned on top. Cool 15 minutes before serving.