Cut the meat against the grain into 5mm-thick slices, removing any silverskin or gristle as you go. Mix all the marinade ingredients in a non-reactive container, then add the meat and toss to coat. Leave to marinate for at least two hours (and up to two days).
For the dressing, mix the first five ingredients in a small bowl. In a separate small bowl, mix the spring onions, chilli, peanuts and pumpkin seeds. Add half this mixture to the soy sauce mixture and set the rest aside – you’ll use it as a garnish.
Drain the meat in a sieve set over a medium saucepan to catch the marinade in the pan; discard the aromatics. Put the marinade on a medium-high heat, bring to a simmer and cook for about three minutes, until reduced and thickened to the consistency of a glaze.
Thread the meat on to the soaked skewers (about 80g meat per skewer), then brush with a little oil and grill on the barbecue for about four minutes, turning a few times and basting with the reserved glaze until the meat has deep char marks and is golden brown all over. Leave to rest for a few minutes, then transfer to a serving plate.
Drizzle the dressing over the meat, sprinkle the reserved herb and peanut mixture on top, and serve hot.