A saying originating in New Zealand.
You would say it when someone or something is disorganized.
It references how cheap biscuit (Cookie) mixes can be messy and difficult to use.
Situation1:
Person1: "Josh forgot to bring his laptop again!"
Person2: "He's all over the place like a cheap biscuit mix"
Situation2:
Person1: "This office is all over the place like a cheap biscuit mix!"