Make the roasted rice powder by dry toasting the uncooked rice in a heavy based pan over a medium heat. Continually move the rice so that the grains turn a deep golden brown and smell toasty and nutty, for around 5 mins. Transfer to a granite mortar and pestle, then grind into a somewhat coarse powder. This will keep for a few weeks in an airtight container.
Combine all the marinade ingredients together and mix well. Add the Irish sirloin and leave to marinate for 3 hours.
Combine lime juice, fish sauce, sugar and roasted chilli powder to create a dressing. This should taste spicy, sour and salty.
Combine the coriander, mint, spring onions, red onion, lemongrass and kaffir lime leaf together in a mixing bowl, add enough dressing to nicely coat the salad without drowning and gently toss together.
Grill the Irish sirloin over a medium-high heat to give nice caramelisation and colour. Allow the meat to rest well before thinly slicing against the grain.
Arrange the sliced sirloin on a plate and pour over a little of the dressing. Arrange the herbal salad over the sirloin, then garnish with roasted rice powder, ready to serve.