Cook the noodles in a large saucepan of rapidly boiling water for 5 minutes, or until tender.
Drain and cover to keep warm.
Combine 1 litre / 35 fl oz water and the dashi granules in a large pan and bring to the boil.
Add the leeks, then reduce the heat and simmer for 5 minutes. Add the pork, shoyu, mirin and
lengths of spring onion and simmer for 2 minutes, or until the pork is cooked.
Divide the noodles among four serving bowls and ladle the soup over the top. Garnish with the
chopped spring onion and sprinkle the shichimi togarashi over the top.