Halve and deseed the chillies, trim and halve the spring onions, then very finely slice the chillies and spring onions lengthways and place into a bowl of iced water until they curl. Put to one side.
Shred the cooked chicken into a bowl. Finely slice the coriander (stalks and all) and add to the bowl, then mix in the grated ginger, barbecue sauce and a good squeeze of lime juice, then set aside.
Place the flour, coconut milk or semi-skimmed milk and a good pinch salt into a food processor, then pulse a few times until you have a sticky dough. Transfer to a flour-dusted work surface and shape into a long sausage, adding a little more flour if it’s too sticky. Cut into 16 equal-sized pieces, then flatten or roll each into circles (roughly ½ cm thick).
Equally divide the chicken mixture between each of the 16 dough circles (you’ll need roughly 1 heaped teaspoon of chicken per circle), making sure to leave a 2cm gap around the edges. Pull and fold the sides over the filling, pinching the edges together to seal. Place the dim sum balls, upside-down in double-layered, lightly greased muffin cases and divide between two bamboo steamer baskets.
Place a wok on a high heat and fill with 2cm worth of boiling water. Once boiling, place the baskets on top of the wok and cover with a lid. Steam for 12 minutes or until light, fluffy and cooked through.
Drain and scatter over the spring onions and chillies, sprinkle with toasted sesame seeds and serve with a bowl of lime-spiked hoisin sauce for dipping.