We present a method for the formation of noble metal nanoparticle ensembles in nanostructured silicon. The key idea is based on the unique property of the large reduction potential of extended internal hydrogen-terminated porous silicon surfaces. The process of metal nanoparticle formation in porous silicon was experimentally traced using their optical plasmon resonance response. We also demonstrate that bimetallic compounds can be formed in porous silicon and that their composition can be controlled using this technique. Experimental results were found to contradict partially with considerations based on Mie theory.