Okay, so technically *not* a proper DF illumination setup, but the results are the same.
This is a perfect example of "killing the ambient" that David Hobby talks about. This was shot in my home office with the window blinds wide open and a pretty sun-lit room.
(I am loving the fact that I can now sync at 1/200sec)
Looking at this the flash is barely visible over the top of the liquid. I think a gobo would be better for the next shot - but I'm thirsty, and the tea is cold and strong...
Strobist: 580EX II M 1/8 @105mm via PW+2, 6" behind pitcher. ISO100 f:1:32 1/200sec