Mr I,
I got this shot from Seve if I remember correctly. have used it to good effect a few times.
Use a PW or any wedge you can open the blade wide, but not have the back of the sole of the club hit the ground first when you swing, i.e. if you open a SW wide and then sit it on the ground, it will be sitting on the tail of the flange of the club. That's no good.
With a PW or other wedge you should be able to open the blade, but the club will sit on the ground with the leading edge of the flange. Perfect.
Anyway, the technique is this:
The objective is to smack the underside flange of the club into the ground right behind the ball. Because you are hitting the ground with the flange the club will then slide under the ball. Bit like a mini flop shot, but be aggressive when you hit the ground.
The angle you hit into the ground should not be too shallow.
With the blade well open (and your stance, setup etc - like a bunker shot) the ball will pop almost straight upwards.
Practice it sometime to get an idea of backswing length etc etc....