In a large bowl, toss potatoes with onion, salt and pepper. In a small cast-iron or other heavy skillet, heat 2 teaspoons oil over medium heat. Add 1 cup potato mixture, pressing down to flatten with spatula. Cook, without stirring, until bottom is golden brown, 4-5 minutes. Drizzle with 1 teaspoon oil; flip. Cook until bottom is golden brown, 4-5 minutes, sprinkling with 2 tablespoons cheese and 2 tablespoons bacon during the last minute of cooking. , Fold hash browns in half; slide onto plate and keep warm. Repeat with remaining ingredients. Top with sour cream and green onions.