Yuzu Shio Ramen

Steps

1. The day before, make the chashu. Heat the oven to 300°F (150°C). Lay the pork belly flat, meat side up, and roll it up tightly lengthwise, fat on the outside, into a log about 3 inches (7 cm) across. Tie it every 3/4 inch (2 cm) with kitchen twine, pulling hard: the meat shrinks as it cooks and a loose roll falls apart when you slice it.
2. In a Dutch oven just slightly wider than the roll, heat 1 tablespoon of the oil over medium-high heat and brown the chashu on all sides for 8 to 10 minutes, until the fat is golden and crisp in spots. Pour off the excess fat, then add the soy sauce, 60 ml of the sake, 60 ml of the mirin, the sugar, and 400 ml of the water. Add 20 g of the ginger, sliced, 3 smashed garlic cloves, and the green part of the leek. Bring to a simmer, cover, and braise in the oven for 2 1/2 hours, turning the roll every 30 minutes: it is ready when a skewer slides in with no resistance at all.
3. Take the pot out and let the chashu cool in its liquid for 1 hour. Meanwhile, bring a saucepan of water to a boil, gently lower in the eggs straight from the fridge, and cook at a gentle boil for 6 minutes 30 seconds. Move them right away to a bowl of ice water for 5 minutes, then peel them under running water. Strain 200 ml of the lukewarm braising liquid, dilute it with 100 ml of the water, and add the eggs, in a zip-top bag with the air pressed out so they stay submerged. Refrigerate for 8 to 12 hours, along with the chashu in the rest of its liquid.
4. For the broth, which you can make the day before or that morning: put the chicken carcasses and wings in a large stockpot, cover with cold water, and bring to a boil. Boil for 5 minutes, until gray foam covers the surface, then drain. Rinse each piece under cold water, pulling off blood clots and any organ bits stuck to the bones, and wash the pot.
5. Return the bones to the clean pot with 3 liters of the cold water, 30 g of the ginger, sliced, the white part of the leek cut into chunks, and 2 smashed garlic cloves. Heat over medium until it starts to shiver, then adjust the heat so a single bubble breaks the surface every one or two seconds, around 195°F (90°C). Cook uncovered for 3 hours, without stirring and without ever letting it boil, skimming during the first half hour. Broth that boils emulsifies and turns milky: for shio ramen, it has to stay clear.
6. Strain the broth through a fine sieve without pressing on the bones: you should have about 1.8 liters. Ladle off 3 tablespoons of the yellow fat floating on top and save it for the yuzu oil (if the broth spent the night in the fridge, the fat lifts off in a sheet). Let the broth cool off the heat to 150°F (65°C), 10 to 15 minutes, add 15 g of the kombu wiped clean, and hold it at 140 to 150°F (60 to 65°C) for 20 minutes over the lowest heat. Remove the kombu, bring the broth up to 185°F (85°C), turn off the heat, add the bonito flakes, and steep for 5 minutes, until they sink. Strain through a damp thin kitchen towel without wringing it.
7. Make the shio tare. In a small saucepan, bring 60 ml of the sake and 30 ml of the mirin to a boil and boil for 1 minute to cook off the alcohol. Add 120 ml of the water, the salt, and the remaining 5 g of kombu, and heat, stirring, without boiling, until the salt has completely dissolved. Turn off the heat, steep for 30 minutes, and remove the kombu.
8. Wash the yuzu. With a vegetable peeler, take 8 thin strips of yellow zest from one of them, leaving the bitter white pith behind, and set them aside for serving. Finely grate all the zest from the second one. Heat 80 ml of the oil with the saved chicken fat to 165°F (75°C) (the oil barely shimmers and nothing sizzles), take it off the heat, add the grated zest, and steep for 20 minutes. Squeeze the grated yuzu and add 1 tablespoon of its juice to the tare.
9. On serving day, lift the chashu out of its liquid, remove the twine, and cut 8 slices 1/3 inch (8 mm) thick with a sharp knife: cold, the roll slices cleanly. Sear them in a very hot dry skillet for 1 minute per side, until the fat sizzles and the edges caramelize. Drain the eggs and halve them lengthwise with a wet knife. Cut each nori sheet in half, finely slice the green onions, and take the menma out of its jar so it comes to room temperature.
10. Reheat the broth over medium heat to 205°F (95°C), just below a boil. Bring 4 liters of unsalted water to a rolling boil in a large pot and fill the bowls with boiling water to warm them. Empty them, then add 35 ml of tare and 1 tablespoon of yuzu oil with a little of its zest to each one. Drop in the noodles, shaking them loose, and cook for 1 1/2 to 2 minutes depending on thickness: they should still have some bite.
11. While the noodles cook, pour 350 ml of piping hot broth into each bowl and stir it into the tare; taste and add a splash more tare if it needs salt. Drain the noodles, shaking the strainer hard since leftover water would dilute the broth, and slide them into the bowls, folding them with chopsticks into a smooth nest. Top each bowl with 2 slices of chashu, 2 egg halves yolk side up, a small handful of menma, a half sheet of nori tucked against the rim, the green onions, and 2 strips of yuzu zest. Serve right away: the noodles keep swelling in the broth.