Select good specimens from the market. They should be firm. Get them from older dealers, who know and nose the good ones. Crack and peel the shells. Get as much of the calculus as you can with your thumbs without bruising the flesh. Leave the shells and husks for the scavengers. The trick is to fold them clean about themselves without corners. Warm them. Then they unfold and crackle. It's better than you might remember.