In a medium mixing bowl combine the ingredients for the marinade, check the seasoning and adjust if needed.
Cut the sirloin into 2-3cm chunks and place into the marinade and allow to sit for at least ten minutes.
Meanwhile thinly shave cucumber and dress in lime juice, palm sugar and fish sauce. Separate the leaves of the iceberg lettuce.
Preheat the griddle pan or bbq. thread the beef onto 4-6 bamboo skewers and cook over high heat constantly turning until cooked to medium rare, 4 minutes. while cooking glaze the skewers in the leftover marinade.
Remove the beef skewers and rest for 2-3 minutes.
Assemble all the ingredients onto a platter and dress with a scattering of fresh red chilli and toasted peanuts.