Dealloying is a selective corrosion process during which the more electrochemically active elements in a parent alloy dissolve while the remaining more noble atoms diffuse along the solid-electrolyte interface, resulting in the formation of a nanoporous microstructure composed of core-shell ligaments. In this work, we study an extension of the physics of dealloying in which the parent alloys (Cu-Fe-Mn alloys) contained an engineered composition of elements selected such that, upon dissolution of one of them, the remaining elements phase separate as they become concentrated in the undissolved ligaments. Such simultaneous dealloying and phase separation leads to the formation of rich variety of new porous structures containing nanocomposite ligaments, as well as unanticipated structure evolution such as nanowire growth that are attributed to solution side effects.