Hello
The breakfast bar was simply screwed to the unit carcasses below. There were 4 points to screw in to so 8 large screws were used.
Hope this helps!

Thanks for the answer. I've got a bit of a different scenario going on since my breakfast bar is going to mount onto a pony wall. Since you have a cabinet it's great you can just go inside and screw in, but i'm trying to figure out how i could do it =). your pic looks awesome btw. does it support a great deal of weight?