Pound the coriander seed, white pepper and cumin in the mortar and pestle to yield a powder.
Add the lemongrass and the pinch of salt. Pound until smooth. (The salt acts as an abrasive)
Add galangal and pound until smooth
Add cilantro roots and pound until smooth
Repeat with the rest of the ingredients, pounding ingredients one or two at a time in the order shown in the ingredients list. If the mortar gets too full, remove a portion of the paste once it is smooth and then combine everything at the end when everything is smooth.
Paste is finished when everything is relatively smooth.
Paste will keep for 3-4 days in the fridge.