They’d have to scan it in first, but perhaps they have already?

Edit: there seems to be some debate as to the quality of replicated food, even within Trek. Personally, I think it depends on a number of variables including the quality of the sample scanned in, the quality and working order of the replicator used to replicate food, etc. Not all replicators are equal.

Also, one can replicate ingredients and then use a replicator to cook a dish as one would in a normal kitchen (although how is unclear), potentially creating a better (or worse) version of a dish with nuance and a personal touch. We have seen Janeway attempt this with various degrees of success— or, more often, failure.