Chashu (see the shoyu recipe), soft eggs, sliced scallions, pickled ginger, sesame seeds
How to make it
Blanch (20 min): Cover the bones with cold water, bring to a boil, boil 10 minutes, drain and scrub off the grey scum and dark bits under running water. This keeps the broth clean-tasting.
Boil hard (10 to 12 hr): Return the bones to a clean pot with 6 liters (6 quarts) water and keep it at a rolling boil, lid ajar. Top up with boiling water every hour to keep the bones covered. The hard boil is what emulsifies the fat and collagen into a white broth. Add the onion, garlic, ginger and leeks for the last 2 hours.
Strain (10 min): Strain through a fine sieve, pressing the bones. You want about 3 liters of thick, opaque broth. If it's thin, boil it down; if it's like glue, loosen with water.
Mayu (15 min, optional): Cook the garlic slowly in the oil, stirring, until it goes past brown to black, about 10 minutes. Off the heat, blend with the sesame oil until smooth.
Bowls (5 min): Mix the tare. Put 2 tbsp in each warmed bowl, add 400 ml (1 2/3 cups) boiling broth and whisk. Cook the thin noodles 45 to 60 seconds (they should stay firm), drain hard, add, and top with chashu, egg, scallions, ginger, sesame and a swirl of mayu.
Tips
In Hakata you order kaedama, a second serving of noodles, into the leftover broth; cook extra.
A pressure cooker gets you there in 2 hours on high.