It is called lollipopping..
Typically you cut off most of the growth on the lower 3rd of the plant in weeks 1 & 3 of bloom so it focuses completely on the Colas.
There are several good threads stickied about growing a pound every 2 weeks or so in another forum by Al B. Fuct, I think it is hydroponics. Anyway, that guy uses the SOG lollipop type grow.