(Photo credit: Alien Ted)
‘Let me get back to you on this one. I need to chew it over‘.
To chew over means to think about the matter carefully before making a decision.
More examples:
– Councils chew over gum tax plan (BBC). Can you even get a pun-less newspaper headline these days?
– Something to chew over (The Economist).
Confessions of the Linguistic Spy 
This reminds me of a Greek friend who would say “Hold on, I’m brewing!!” when she meant “Hold on, let me think…” It would crack me up every time 😀