Turn the crab over so it rests on its shell. Remove the bottom flap, pull out and discard the ‘dead man’s fingers’ and cut each crab in half. If they are large, cut into manageable pieces.
Mix with all the aromatics in a bowl. Bring a pot of water to the boil and arrange a steamer on top. Arrange half the crabs in a shallow bowl and place in the steamer basket. Cover and steam for 6 minutes, or until cooked.
Carefully remove the bowl, taking care not to lose the tasty juices in the bottom. Repeat with the remaining crabs and serve straightaway. If you have a large steamer or use a wok, you can cook the crabs all at once.