For the curry paste, finely chop the coriander stalks and put them into a mini food blender or small food processor with the shallots, lemongrass, garlic and galangal. Pulse until as smooth as you can get it. Add the chillies, basil, threequarters of the coriander leaves, the ground cumin, pepper, lime leaves and lime juice, then pulse again. Mix in the oil. Transfer to a glass or china dish, cover tightly (otherwise it will taint everything in the fridge) and refrigerate (ideally for about 6 hours).