Clean the crabs well.
Heat a little oil in a pan.
Fry chicken masala, chilly powder, coriander powder and turmeric powder.
Marinate the crabs with this mix for 20 - 30 mins.
Heat oil in the pan.
Splutter mustard seeds.
Add curry leaves and onions and fry.
When the onions are fried, put the crabs into it.
Add salt and heat, till it gets cooked well(maximum 20 mins).
Add coconut milk, just before removing from heat.
:- For better taste, serve after one hour.