Place the peeled and chopped potatoes into a large pot, cover with cold water, and bring to a boil over medium heat. Cook until tender, about 15-20 minutes. Drain and set aside.

In a skillet, heat a tablespoon of oil over medium heat. Add the finely chopped onion and sauté until translucent, about 3-5 minutes. Add the ground meat, breaking it up with a spatula, and cook until browned. Stir in the soy sauce, then season with salt and pepper to your liking.

In a mixing bowl, mash the drained potatoes until smooth. Fold in the meat and onion mixture and mix well. Allow the mixture to cool slightly.

Once cooled, form the potato mixture into patties or ovals about 1/2 inch thick.

Set up three bowls for coating: one with flour, one with beaten eggs, and one with panko breadcrumbs. Dredge each patty in flour, dip into the egg, and finally coat with panko, pressing gently to adhere.

In a heavy-bottomed skillet, heat about 1 inch of oil over medium-high heat. Carefully place the croquettes into the oil in batches, frying until golden brown on both sides, about 3-4 minutes per side.

Remove the croquettes from the oil and place on paper towels to drain excess oil. Serve hot with your choice of dipping sauces, like ketchup or tonkatsu sauce.