Add all the laab spices to a heavy bottom pan and toast over a low heat until fragrant. Grind to a fine powder in a stone pestle and mortar or spice grinder.
Roll the Irish fillet in the laab spice powder ensuring it is completely coated.
Pound the chillies, garlic and coriander root in a stone pestle and mortar until a smooth paste. Add the sugar, lime juice and fish sauce then combine well. Taste the dressing, it should taste spicy, sour and salty. Add the finely chopped coriander and mix together.
Over a high heat sear the Irish fillet on all sides. You want to develop a nice dark crust to seal in all the meat juices and create a caramelised outside, almost blackened and burnt for a contrast in flavour.
Set the Irish fillet aside for 5 minutes to rest then slice thinly, ensuring there is a layer of seared edge on each slice. Arrange on a serving plate and spoon over the dressing, ready to serve.