Nanostructures with broken symmetry can interact with circularly polarized light to mimic chiroptical (chiral-optical) effects, usually observable in chiral media. This phenomenon is known as extrinsic chirality. Second harmonic generation (SHG) is extremely sensitive to symmetry breaking, down to a single atomic monolayer and it has been extensively used as a probe of extrinsic chirality. Here we present SHG measurements of GaAs nanowires partially covered with Au, fabricated by a self-catalysed technique. The Au coated GaAs nanowires give rise to a dramatic circular dichroism in the generated second harmonic signal, compared to nanowires without coating.