Peel and grate the potatoes, then transfer them to a cheesecloth-lined bowl. Firmly wring out all excess moisture using the cheesecloth or by squeezing handfuls dry and blotting with paper towels. Mix in the onion powder until well incorporated.

Heat a 10-inch cast-iron or nonstick skillet over medium heat. When the skillet is hot but not smoking, add 1 tablespoon of oil or bacon fat, followed by 1 tablespoon of butter, swirling them together.

Spread the grated potatoes in a uniform layer about 1/3-inch thick. Let them cook undisturbed for 6 minutes, allowing the bottom to develop a crisp, golden crust. If browning too rapidly, reduce the heat.

Season the top with sea salt and freshly ground pepper.

Carefully flip the hash browns. If a single flip is difficult, divide them into halves or quarters using a pizza cutter and turn the sections individually.

Add the remaining tablespoon of oil or bacon fat around the edges and place small dots of the remaining butter near the edges so it melts underneath. Continue sautéing without stirring for another 6 minutes, until the second side is also crispy and golden.

Remove from heat and garnish with chives, if using. Serve promptly.