Pound the spice paste ingredients in a mortar with a pestle to a fine paste. Or use a blender to process the ingredients, adding
Heat a wok until just smoking. Add the oil and, when hot, add the spice paste and stir-fry for about 5 minutes, or until the rawness has been cooked out and the paste becomes fragrant. Add
Meanwhile, steam the yams over a pot or a wok of boiling water for 15–20 minutes, or until tender. Stir the yams into the curry, then season with palm sugar, fish sauce and lime juice to serve.