Possible Clues:

• Leaving no opportunity for error
• Can't go wrong when pudding has some alcohol content
• Certain if left and right swapped, the other way up is the same
• Guaranteed
• A pudding and its eating? It's sure to go well
• Infallible pudding and its eating?
• Not liable to failure
• Can't go wrong with this trick at Confirmation
• This is why you won't get this as a security precaution
• Very simple pudding and what eating it constitutes?