He then joined the Addicks in January and is beginning to settle into the first team.
"Charlton's an option for me," Cook told the South London Press.
"Ever since I've been here, I've been trying to impress the manager and, if Charlton made an offer for me and Fulham were willing to let me go, then of course I'd be interested.
"The ball's in Fulham's court, though. If they want me to stay with them then I'm more than happy to do so, but that's something to think about in a few weeks' time, not now."