1. Make the dipping sauce. Bring the sugar and vinegar to the boil, add the soy sauce, remove from the heat and allow to go cold.
2. Add the chilli oil and sesame oil.
3. Season with a little salt and store in an airtight container until ready to use.
4. Heat the oil in a large frying pan over a medium heat.
5. Arrange the dumplings in rows in the pan and fry at a medium heat until crispy and golden brown on one side. Turn them over, cook for a short while, then pour over the hot water. Quickly cover with a lid to keep in the steam. Leave the dumplings to steam until cooked, about 3-4 minutes.
6. Arrange the dumplings on a serving plate, drizzle over a little sesame oil, scatter over the sesame seeds and serve with the dipping sauce on the side.