Fill a large pot with water, about 1 inch deep, and bring it to a simmer over medium heat. Arrange the potatoes in a steamer basket in an even layer. Cover and cook until the potatoes are softened but not mushy, about 10 to 15 minutes.
Transfer the potatoes to a baking sheet and spread them out evenly. Let them cool for about 20 minutes.
Transfer the potatoes to a medium bowl. Add potato starch, salt, sugar, and pepper, and toss to combine.
Shape the potato mixture into 6 patties, each about 2.5 ounces and 3 1/2 inches by 2 1/2 inches, ensuring the edges are flattened and rounded. Place them on a parchment-lined baking sheet and freeze for at least 1 hour or up to 24 hours.
In a large, heavy pot fitted with a deep-fry thermometer, pour in enough oil to reach a depth of 1 inch. Heat over medium heat until the thermometer registers 350°F. Fry the hash browns, flipping halfway through, until lightly golden brown, about 10 minutes. Transfer to a wire rack set in a baking sheet and let them cool slightly. Enjoy your homemade hash browns!