Direct laser writing and subsequent electroless silver plating is introduced as a high-quality fabrication method for three-dimensional plasmonic nanostructures. With this method, we fabricate the first three-dimensional bichiral plasmonic crystals, which exhibit a large difference in transmittance of left-handed and right-handed circularly polarized light in the mid-infrared spectral region between 3 and 5 mu m. Our structure has a high degree of isotropy, showing only a weak dependence of the transmittance on the angle of incidence.