In a frying pan, dry-fry the coriander seeds and cloves over a medium heat for a few minutes, then add the cumin seeds, heating them for another 30 seconds. Grind in a clean coffee grinder or mortar, then put this mixure with the remainder of the masala ingredients into a food processor and blend to a paste. If the masala paste is too stiff add a little vegetable oil to loosen it.
Fry the masala in the vegetable oil until the spices separate from the oil.
Wash the mussels, clams and cockles and toss them in the masala paste then cover with a lid and, shaking from time to time, steam cook until the shells open. If you feel the mussels haven't produced enough liquid add a little water. The recipe contains no salt as mussels are salty, but taste to check the seasoning. Throw in a generous amount of chopped coriander and serve in bowls.