01 -
Boil peeled and quartered potatoes in water until tender, about 20-25 minutes. Drain thoroughly, return to pot while warm, and mash until smooth. Mix in butter until melted and set aside.
02 -
Heat oil in a skillet over medium heat. Sauté minced onion until soft, 3-4 minutes. Add ground beef, breaking it up while cooking. Stir in soy sauce, sugar, and black pepper. Cook until beef is browned, another 3-4 minutes.
03 -
Combine the beef mixture with mashed potatoes, stirring well. Season with salt and pepper to taste. Let cool until warm enough to handle.
04 -
Shape the mixture into oval patties about 1 inch thick and 3 inches long. Place on a baking sheet, cover with plastic wrap, and refrigerate for at least 30 minutes to firm up.
05 -
Set up three stations: flour on a plate, beaten eggs in a bowl, and panko on another plate. Coat each patty in flour, then egg, then panko, ensuring complete coverage.
06 -
Heat oil to 340°F in a medium saucepan to 1½ inches depth. Fry patties in small batches for about 3 minutes, flipping once, until golden brown. Drain on a wire rack or paper towels.