Kroeung is traditionally made by finely chopping the ingredients and grinding them together using a heavy mortar and pestle although mechanical food processors can be used in modern kitchens.
[2] This herbal paste is essential for preparing Khmer dishes in order to create the authentic flavour.
Traditionally, kroeung recipes, specifically for curries, requires whole spices to be ground with the herb paste.
The difference between royal and individual kroeung is the extra ingredients sometimes used to make the paste, coriander and Kaffir Lime leaves (instead of zest).
Red kroeung (Khmer: គ្រឿងក្រហម, krœăng krâhâm) receives its deep color from a type of dehydrated chili pod which contributes very little flavor to the kroeung and is added solely for the natural red color, although as the dish is meant to be spicy, hotter chilli peppers may also be used in the spice paste.
The ingredients are then added to the mortar and pounded, usually lime zest/leaves first until smooth, then chili, lemongrass, galangal, and turmeric, until a deep red color is achieved.
The usual ingredients for a green kroeung are lemongrass (about a three to one ratio of leaves to stalks), rhizome, cinnamon, galangal and turmeric.
A version with prahok, minus the cinnamon, is called teuk kroeung and used as a dipping condiment for fresh or slightly blanched vegetables eaten with rice either as a side dish or as a meal in itself.