Much like the shrimp paste used in Chinese cookery, crayfish (actually dried shrimp) is used as a flavouring (and a thickener) for many stews and soups. Chinese shrimp paste may be used as a substitute. 

Small crayfish is ground whole using a coffee mill  or  blender; or more  traditionally using a mortar or grinding stone. Larger ones may be used whole – remove the heads, tails and legs (these can also be ground and used for cooking), and add to soups or casseroles to cook until fairly tender. 

Crayfish may be bought whole or already ground and should be stored in an airtight container in a cool, dry place.

Whole Small Crayfish

Whole Large Crayfish