The Butterfly pole dance trick is a pretty inversion that is considered an advanced trick. You need to have a strong and controlled basic invert and heed to all pole dance safety guidelines when attempting this move. A spotter and/or crash mat should be used as well.
This inversion can also be learned first from the floor so that you feel the points of contact and where the pressure will be on your calf, inside of thigh and the way your body weight feels held in that position.
Here is a video clip of the move being performed:
This move is basically like the Butterfly Extended, except for extending your leg out straight, you bend your foot towards your body, like a hook.