Gordon Ramsay -- I'm NOT Turning My Back On Ja'Nel Witt ... Even After Positive Coke Test

Chef Gordon Ramsay tells TMZ ... he isn't writing off disgraced "Hell's Kitchen" champ Ja'Nel Witt even after she failed a drug test -- "My door is always open."

We broke the story ... Witt was not allowed to take the job as head chef at Ramsay's Las Vegas restaurant after winning HK earlier this year because she tested positive for cocaine.

But Ramsay says he still believes in Witt's talent ... and yesterday at LAX he told us, "I hope she sorts out her personal issues."