pig trotters, split lengthwise or cut into 1in disks • chicken backs and carcasses, skin and excess fat remove • vegetable oil • large onion, skin on, roughly chopped • garlic cloves crushed skin on • knob ginger, roughly chopped • whole leeks, washed and roughly chopped • scallions, white parts only (reserve greens and light gr • whole mushrooms or mushroom scraps • slab pork fat back