Coarsely grate the potatoes and onion. Place into a colander in the sink and allow to drain of excess liquid for about 30 minutes. Use a paper towel to press out any excess liquid as needed.
To a large bowl, add potatoes, onion, flour, egg, salt, and pepper. Mix thoroughly.
Heat a 12-inch skillet over medium-low heat with 1 Tablespoon of oil and 1 Tablespoon butter. Use a 1/4 cup measurement to scoop potato mixture and form into loose patties about 1/4 inch in thickness. Work in batches to fry in the skillet 4 minutes on each side until golden brown.
Repeat the process in three batches.
To keep previous batches warm and crunchy, place on a baking sheet in an oven set to warm or 200F.
Use whatever potatoes you would like. Wash and clean the skin or peel. Yukon Golds used here are a very clean potato and easy to leave the skin on and eat.