1. Peel the potatoes if desired, then shred them using a large-holed cheese grater or food processor.
2. Place the shredded potatoes in a colander and rinse thoroughly under cold water until the water runs clear to remove excess starch.
3. Drain well and then remove as much moisture as possible by pressing the potatoes against the colander sides, squeezing by hand, or wrapping in a clean lint-free dish towel or cheesecloth and pressing to dry.
4. Toss the dried shredded potatoes with onion powder for extra flavor if desired.
5. Heat a large cast iron or non-stick skillet over medium heat until hot but not smoking. Add about 1 tablespoon of cooking oil, tilting the skillet to coat evenly.
6. Spread about one-third of the shredded potatoes in a thin, even layer about 1/3 to 1/2 inch thick in the skillet. Press lightly to compact.
7. Cook undisturbed for 3 to 6 minutes until the bottom is deeply golden brown and crispy. If browning too quickly, reduce heat slightly.
8. Season lightly with seasoning salt and freshly ground black pepper.
9. Carefully flip the hash browns to cook the other side. Add more oil or butter as needed.
10. Cook the second side undisturbed for another 3 to 6 minutes until golden and crispy.
11. Repeat the process with the remaining shredded potatoes in batches, adding oil as needed.
12. Serve hot, optionally garnished with fresh chives or your preferred toppings.