Put the paste ingredients in a small food processor and pulse until you get a coarse paste.
Heat a drop of sesame oil in a large frying pan or wok. Add the pork mince and stir-fry for about 8 mins until brown. Move to a plate, discard the liquid. Add the remaining oil to the wok and stir-fry the paste for a minute or so then put back the pork. Add the fish sauce, sugar and juice of ½ lime. Stir until the pork starts to caramelise.
Remove from the heat and add the chopped herbs and spring onion. Mix well.
Lay the salad leaves on a large serving platter and spoon some mince into each lettuce cups. Drizzle with sweet chilli sauce and scatter some coriander leaves all over them.
Serve with the lime wedges.