Place the duck legs in a roasting tin. Mix together the water, soy sauce, mirin and rice wine and pour over the duck legs. Roast for 1 and a half hours in a 180°C oven.
Once the duck legs have finished cooking, remove them from the oven and leave to cool for a couple of minutes. Shred the meat, it should be falling off the bone. While that's happening place the pak choi in the roasting tin cut side down and place in the hot oven for 5 minutes to get a little charred.
Assemble your bowls. Place half the rice in each bowl and top with all your toppings. Finish with a drizzle of the duck roasting juices.