Ingredinets:

Crabs 4(big) 8 if Small
Medium Onions
Small Coconut
1 tea spoon Coriander seeds
5-6 Red chillies
Small Ball of Tamarind
Oil 2 tea spoons
Salt

Method:

Clean the crabs. If the crab is big, cut them into 2 pieces to make eating easier.
Slightly crush the legs with pestle(beat it just once or twice just to crack the outer shell slightly).
if its small then you can remove its legs
Heat 1 tea spoon of oil and fry coriander seeds. Grind them with red chllies, coconut and tamarind to a smooth paste.
Heat remaining oil and fry onions till they are slightly brownish. Add ground masala, salt and cook for 2-3 min.
Now add the crabs and cook for around 10-15min.
Serve hot with rice.