Blend onions, garlic, chillies, fresh turmeric and fresh galangal with some water until you get a pale yellow paste.
Heat oil and fry paste until fragrant (pecah minyak). Put in lemongrass (that has been bruised), dried tamarind and turmeric leaf and stir it in.
Add brown sugar and after that is well mixed, pour in the coconut cream. Let it simmer for 5 minutes then put in the crabs, add salt to taste.
Close the lid so that the sweetness of the crabs will infuse the gravy.
Let it steam and simmer for 10 minutes.