1Carefully trim the fatty base and tip from the Beef tongue. Peel off the tough outer skin completely. Slice the prepared Beef tongue thinly, about 3-5mm thick, against the grain.
2In a bowl, combine Soy sauce (koikuchi), Mirin, Sake, finely grated Garlic, finely grated Ginger, and Sesame oil to create the marinade. Add the sliced Beef tongue to the marinade, ensuring all pieces are coated. Marinate for at least 30 minutes, or up to 2 hours in the refrigerator.