A single-breasted jacket with peak lapels and one button.
Is this combination strictly black tie? Or is a fold-down shirt collar, necktie and lighter jacket colour enough to make it informal (as opposed to casual)?
The buttoning stance should be the same for a one button suit or two button suit. I don't really understand how adding an additional button that you never button makes a huge difference in how an outfit is viewed. I do think that the peak lapels are much more obvious. That said, a peak lapel one button suit could be a lovely choice in a nice navy color to wear to things like weddings and evening events that are just shy of black tie. I wouldn't try to make it work with a button down color or light jacket, though.