In a food processor (on the shredding/grating setting), process your cabbage, leek and carrot. Alternatively, finely grate the carrot then thinly slice and leek and cabbage.
Heat 1 tsp of oil in a frying pan or wok, then stir fry the shredded vegetables, ginger, garlicĀ and half the chilli for a couple of minutes until soft. Stir through the soy sauce and cook for a minute until the liquid has evaporated.
Transfer to a bowl and chill in the fridge.
Lay out your gyoza wrappers. Have a small bowl of cold water to hand. Using your finger, gently wet the edge of the gyoza wrapper, place a teaspoon or two of the filling in the centre then seal your gyoza.
Heat the remaining oil in a large deep frying pan on a medium to high heat and lay out your gyoza gently in the pan and fry base side down for 2-3 minutes, then on their side to brown off the edge. Once you have a golden brown gyoza, lift each one so the base side is sitting on the frying pan and add 2 cm of warm water to the pan and steam the gyoza until the water has evaporated.
Serve immediately with a pot of soy sauce for dipping, and a scattering of the remaining sliced chilli, the sliced spring onions and sesame seeds.