Start from the platform with hands turned as if doing a half turn on the bar. At the front, turnaround on the bar and then let go and make another full turn to catch the bar again. Technically this is one-and-a-half twists at the frontend, but in reality it is performed as first a half turn, then a single pirouette.
You can find out more about this trick in my books:
Thanks to Jean Francois and Tristan for sending us this video.