Nature provides unique insights into design strategies evolved by living organisms to construct robust materials with a combination of mechanical properties that are challenging to replicate synthetically. Hereby, inspired by the impact-resistant dactyl club of the stomatopod, we rationally designed and produced a mineralized biocomposite in the complex-shapes of dental implant crowns exhibiting high strength, stiffness, and fracture toughness. This material consists of an expanded helicoidal organization of cellulose nano-crystals (CNCs) mixed with genetically-engineered proteins that regulate both binding to CNCs, as well as in situ growth of reinforcing apatite crystals. Critically, the structural properties emerge from controlled self-assembly across multiple length scales regulated by rational engineering and phase separation of the protein components. This work replicates multiscale biomanufacturing of a model biological material and also offers an innovative platform to synthesize multi-functional biocomposites whose properties can be finely regulated by colloidal self-assembly and engineering of its constitutive protein building blocks.