This paper introduces so called SILHOUETTE platform for electro-optical (E/O) co-integration for high-density hybrid systems. Need for parallel, flexible and scalable system integration approaches demanded by integrated photonics is explained. Platform concept based on co-design of SiN photonic processing unit (PPU), application specific integrated circuit (ASIC) and Si-interposer with optical function introduced by polymeric back end of line (BEOL) is shown. Design and functionality of individual components as well as their co-design is detailed. Processing of Si-interposer with electrical redistribution layer (RDL), pads as well as polymeric waveguides (WGs) and µ-mirrors via hybrid lithography is shown. PPU fabrication on 300 mm wafer with deposition and structuring of SiN for WGs, SiO₂ cladding and TiN for heaters is shown. Cu-RDL, pads and solder bumps are deposited for reflow assembly of PPU. Finally work is concluded and an outlook to future goals of consortium is provided.