Boil 350 ml of water in a pot.
Heat lard and sesame oil in a frying pan, add chopped Japanese leek, and briefly stir-fry for about 10 seconds.
Add the remaining ingredients in the boiling water from Step 1, bring to a boil again, then turn off the heat.
Transfer the soup into a bowl. Add freshly boiled noodles, and scatter the leeks with the oil over the noodles. Top with toppings you like, and it's done.