Put the 500 grams lamb loin in a bowl along with the 14 grams fresh ginger, 7 grams garlic, 2 tablespoons soy sauce, 1 tablespoon sake, 2 teaspoons granulated sugar and 1 teaspoon Japanese curry powder. Stir well to combine, cover and refrigerate for at least 1 hour or or preferably overnight.
When you're ready to fry the lamb, add add 1-inch of vegetable oil to a heavy bottomed pot and preheat to 355 degrees F (180 C). Prepare a wire rack lined with a triple layer of paper towels.
Make the mint sauce by adding the 2 grams mint, 4 grams cilantro, ¼ cup rice vinegar, and 1 tablespoon granulated sugar to a blender or small food processor and puree (you can also use an immersion blender).
When the oil is at the desired temperature, add the ⅓ cup potato starch to a medium bowl and toss the lamb pieces in the potato starch to coat evenly. Carefully drop the lamb into the hot oil and fry in batches until golden brown, turning once to ensure the lamb browns evenly.
Transfer the fried lamb to the prepared rack and serve immediately with the lamb sauce. If you plan to serve this as a canape, just skewer the lamb with decorative picks.