Well, in order to have a monogendered society that is patterned off of the male body, they would have to survive in an entirely parasitic way by completely using other species. That would imply some unpleasant things about how their culture is likely to have developed if you think about it coldly and logically.
So I went back on that and decided they'd have to be hermaphroditic with a male body pattern on the outside. You could even have them follow the asari practice of having a cultural preference for partnering with aliens.
The thing is, do Asari have vaginas? I just imagine that they somehow put their partner in a hypnotic state, where they imagine having real sex, but there is no real thing happening outside of each other's minds.
If these male-not-asari have both sex organs and can produce both gametes as well, then there might be some compatibility issues with other species.
Also, the parasitic nature could be interesting, but not sexy unless they hide it well.