it is a lot like a double up, except you take a sharp turn in the beginning. the sharp turn makes the wake in the corner of the turn really tall. you then drive similar to a double up, with the intent of having the corner of the initial turn meet up with your wake where the rider would normally hit the double up (drive just to the outside of the corner.)
I have included a sketch. In the sketch I have it drawn as a right angle turn, however, if you find that the corner is separating into two waves, take the turn slightly less sharp.
This sends rollers everywhere, and takes a relatively large area to do, so make sure there are no other boats in the area, especially other wakeboarders that like butta.