Add the flour to a mixing bowl with a pinch of salt, then slowly stream in the water, mixing with chopsticks constantly, until you have a shaggy dough. Turn it out, then knead for 8-10 minutes until smooth. Wrap and chill for at least 30 minutes.
Combine the remaining ingredients in a separate bowl. Use your hands to vigorously mix everything together – you want to really break down the mince into more of a paste. Cover and keep in the fridge until needed.
Divide the rested dough into 18 equal balls, about 25g each. Set up a large steamer basket over a pan of simmering water and cut out several discs of baking paper which will fit inside the steamer.
Roll a piece of dough into a circle around 9cm wide, dusting with flour as you work to prevent sticking. Put 1 tbsp of the filling in the centre, then wet the edges of the pastry with a brush and seal (you can simply fold them over, crimp or pleat however you like). Put completed dumplings on the discs of baking paper.
Steam the dumplings in batches for 8-10 minutes. Meanwhile, whisk the dressing ingredients together.
Divide the dumplings between plates with the dressing, then top with springs onions and chilli flakes.
