Rub the pork belly all over with 2 tbsp soy sauce. Let rest at room temperature for 30–60 minutes — the soy enzymes gently tenderise the meat and add subtle seasoning throughout. Then pat completely dry with paper towels.
Heat a dry frying pan over medium-high heat. Sear the pork belly fat-side down for 2 minutes, then each other side for 1 minute, until deeply golden brown on all surfaces.
Transfer the pork to a deep pot. Add 2 litres of water and 5 tbsp uncooked rice. Bring to a boil, then simmer for 60 minutes. Add scallion green at the 30-minute mark. Turn off heat and rest the pork in the cooking water for 90 minutes.
Lift the pork out, rinse off any sticky residue, and cut into roughly 4cm (1.5 inch) cubes.
In a clean pot, combine soy sauce, sake, and sugar. Bring to a boil for 1–2 minutes to cook off the alcohol. Add the pork cubes and simmer 4–5 minutes to glaze.
Add 600ml water, sliced ginger, and peeled garlic. Place a drop lid (otoshibuta) or parchment paper directly on the surface. Simmer for 40–50 minutes, turning the pork once or twice.
Turn off heat. Cover with paper towel and let rest for at least 20 minutes. For best flavour, refrigerate overnight and reheat the next day.
If using soft-boiled eggs, peel them and add to the pot during the final 5–10 minutes of simmering. Serve hot with rice, the soy braising liquid, and a soft-boiled egg per person.
