Method
1
Grate potatoes, soak in cold water 10 minutes, drain and squeeze very dry.
2
Toss with grated onion, salt and pepper.
3
Heat butter in cast iron, press potato mix into a 1/2 inch slab. Cook undisturbed 6 minutes.
4
Flip carefully, cook 5 more minutes until both sides are deeply golden. Shower with chives.