A composite material of plasmonic nanoparticles embedded in the scaffold of nanoporous Silicon offers unmatched capabilities to use it as a SERS substrate. The marriage of these components presents an exclusive combination of tightly focused amplification of Localised Surface Plasmon (LSP) fields inside the material with extremely high surface-to-volume ratio. This provides favourable conditions for a single molecule or extremely low concentration detection by SERS. In this work the advantage of the composite is demonstrated by SERS detection of Methylene Blue at the concentration as low a few picomolars. We systematically investigate the plasmonic properties of the material by imaging its morphology, establishing composition and their effect on the LSP resonance optical spectra.