To begin, rinse the pork bones thoroughly under cold water, then place them in a large pot. Cover with water and bring to a rapid boil for 10 minutes. This removes impurities and ensures a cleaner broth. Drain and rinse the bones well before proceeding to the next step.

Refill the pot with fresh water and return the cleaned bones. Add the onion, garlic, ginger, and leek. Bring to a boil, then lower to a rolling simmer. Skim off any foam for the first 30 minutes to keep the broth clear.

Continue to simmer uncovered for 10–12 hours, topping up with hot water as needed to maintain level. The broth should become creamy and opaque, a sign that the collagen and marrow have emulsified properly. Stir occasionally to prevent sticking.

While the broth cooks, place the rolled pork belly in a saucepan. Add soy sauce, sake, mirin, sugar, garlic, and ginger. Bring to a gentle boil, then reduce to low heat and simmer for 1½ hours, turning the meat occasionally until tender and caramelised. Remove and cool in the liquid before slicing.

In a small pan, combine soy sauce, mirin, sake, and sugar. Bring to a simmer for 5 minutes until slightly reduced. This tare forms the seasoning base that balances the richness of the broth.

Boil the eggs for 6½ minutes, then cool immediately in iced water. Peel carefully and marinate in some of the chashu liquid for 2–3 hours for added flavour.

Once the broth has reached a rich milky consistency, strain it through a fine sieve to remove solids. Return the liquid to the pot and keep warm. Adjust consistency with water if too thick.

Bring a pot of water to a rolling boil and cook the ramen noodles according to the packet instructions, usually 1–2 minutes for fresh noodles. Drain and shake off excess water.

Add 1–2 tablespoons of tare to each serving bowl. Pour in the hot tonkotsu broth and stir to combine. Add the cooked noodles, then top with slices of chashu pork, halved eggs, spring onions, and nori.

Serve immediately while hot. Sprinkle with sesame seeds if desired. Tonkotsu ramen is best enjoyed fresh, with a side of pickled ginger or a drizzle of chilli oil for a touch of heat.