Heat a wok or heavy-based frying pan and, without adding any oil, dry-roast the coriander and cumin seeds for 40–50 seconds until toasted and aromatic. Tip into a spice grinder and grind to a fine powder.
Put the spice powder in a food processor with all the other ingredients and whiz to a paste (add a little water if the mixture is too stiff). Store in a jar in t