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1
Combine the tonkotsu and gyokai broths in a heavy saucepan and reduce over medium heat, stirring occasionally, until the liquid is 3–5× more concentrated than a standard ramen broth — it should coat a spoon heavily and taste almost aggressively savoury. Season with soy sauce and mirin. The broth must be strong enough to flavour thick noodles after only the briefest contact; taste and reduce further if any doubt remains. Hold hot.
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2
Bring a large pot of unsalted water to a full rolling boil. Cook the thick wavy noodles according to their thickness — for 3–4 mm noodles, begin tasting at 3 minutes. The noodles are done when they offer firm, elastic resistance throughout: al dente with no raw core. Overcooking destroys the textural purpose of the format.
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3
Drain the noodles and rinse under cold running water, working quickly with your hands, until all surface starch is removed and the noodles have cooled to room temperature. Do not chill in ice water or refrigerate; the noodles should be cool but not cold. Divide into four equal mounds in four wide shallow bowls. The surface should look dry and slightly sheen, not wet or clumped.
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4
Ladle the hot concentrated dipping broth into four small, deep bowls — one per diner. The bowls should be small enough that a bundle of noodles, when dipped, submerges only ⅓ to ½ of its length. Arrange the chashu, soft-boiled egg, menma and nori alongside the noodle bowl or on a separate plate. The broth should be visibly steaming and deeply coloured.
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5
At the meal's end, bring the jug of plain hot wari broth to the table. Each diner pours the wari into their remaining concentrated dipping broth at their own preferred ratio, converting the residual tsukedare into a light drinking soup. The completed bowl should smell of rendered pork fat and dried fish, with a warmth that signals the designed conclusion of the meal.