Use a mortar and pestle to lightly crush the cumin seeds so you have a mix of powder and crushed seeds. Transfer to a large bowl. Add the lamb, egg, Shaoxing wine, soy sauce, dark soy sauce, ginger and spring onion. Mix vigorously. Place a tablespoon of filling onto the centre of a dumpling wrapper. Moisten the edges of the wrapper with water and fold the wrapper over the filling. Press to seal the wedges. Place the dumpling onto a tray, pushing down to flatten the bottom and create a ‘crimped’ pattern at the top. Repeat with remaining filling and wrappers. Heat the vegetable oil in a large non-stick frying pan over high heat. Add the dumplings and wait about 2 minutes for their bottoms to crisp up and turn golden. Then pour in enough water for come about halfway up the side of the dumpling. Cover with a lid and allow the water to steam and cook the dumpling for about 5 minutes. When the water has almost evaporated, remove the lid and let the pan continue sizzling until the water is completely gone and the dumpling bottoms are super crispy. Transfer the dumplings to a serving plate. Drizzle with chilli oil and serve with soy sauce for dipping.