Does anyone have any good tips on how to sculpt a witch out of molding chocolate to put on an 8 inch cake?

How fancy do you want to make it? For instance for a simple witch I might do a giant pumpkin with 2 legs (dark chocolate with maybe green stripes) sticking out ala the wicked witch of the East in the Wizzard of Oz. Or if you can find a doll tutorial you can do one of those and just give her a black dress, a pointy hat and a broom. Good luck!