Ice cake sides and background smooth. Outline ghost, cauldron and eyes with tip 3; fill in eyes and smooth with finger dipped in cornstarch.

Add tip 4 dot pupils. Outline and fill in mouth and tongue with tip 4; outline tip 4 chin. Cover ghost with tip 21 stars.

Using pattern, cut hat from cake board and cover with foil. Outline hatbrim on cake with tip 3; fill in with tip 18 stars.

Position hat (support back with extra icing). Cover hat, hat band and cauldron with tip 18 stars. Pipe tip 2A string rim on cauldron.

Pipe dot bubbles and splashes of brew with tip 12, smooth with finger dipped in cornstarch. Pipe tip 5 string, message and dot highlights.

Insert pretzel logs at bottom of cauldron. Spatula stripe bag in red, yellow and orange; pipe tip 21 pull-out star flames. Pipe tip 21 star bottom border.

Highlight splashes of brew with decorating gel.