Warm a frying pan over medium heat. Add the coriander seeds, cumin seeds, ground cardamom, cinnamon quills, cloves, white peppercorns, dried red chillies and salt. Cook for several minutes, stirring occasionally, until the chillies blacken and spices are toasted. Transfer to a mortar and set aside.
Wrap the shrimp paste inside a small piece of aluminium foil and fold it over to form a parcel. Place it in the frying pan and toast on medium heat for 1-2 minutes on each side. Remove the shrimp paste from the parcel and set aside.
Heat the oil in the frying pan and cook the shallots, garlic cloves, lemongrass, galangal, kaffir lime leaves and shrimp paste until softened and starting to brown. Remove from the heat and allow to cool.
When cooled, transfer the mixture to the mortar and combine with the toasted spices. Add the lime zest, coriander roots and nutmeg then grind everything until smooth.