Prepare the pork belly: Cut 1kg pork belly into 6cm width x 18cm length (to suit your cooker).
Sear the pork belly: Heat a large frying pan on high heat, add oil and sear the pork skin side down for few minutes on both sides. Remove from the pan and wipe off any excess oil.
Simmer the pork belly: Add 1 litre of water mixed with the ginger and leek into a large saucepan, then add the pork and place the lid on. Bring the pork to the boil and then turn the heat to low and simmer for 1.5 hours. If you are using a pressure cooker instead, simmer for 30 minutes.
Cut the pork belly into large cubes: Remove the saucepan from the heat and drain the liquid from the pork. Let the pork cool for 10 minutes and then cut it into large cubes.
Add seasonings to the broth: Place 400g daikon, peeled and cut into 3cm thick round slices, 1 5cm x 5cm kombu, and a mixture of 50ml shaoxing rice wine, 50ml mirin, 150ml soy sauce, 5 tbsp brown sugar, 3 tbsp tamari soy sauce, and 800ml water to the saucepan and bring to the boil. Add the pork to the saucepan, place the lid on, turn the heat down to low and simmer for 2 hours. If using a pressure cooker, simmer for 45 minutes.
Serve and enjoy: Serve the pork in the sauce with blanched sugar snap peas, spring onions and mustard if you like it hot.