This project investigates how 3D-printed, thin-shell formwork can enable materially efficient bio-composite furniture. The chair is grown from a mycelium-bound substrate that is compacted into a custom-printed biodegradable formwork, which serves simultaneously as mold, moisture-regulating enclosure, and structural constraint during growth. The digitally generated formwork geometry minimizes material usage while ensuring even colonization and drying of the mycelium. After the growth phase, the bio based composite is dried to achieve structural stiffness, resulting in a lightweight, fully bio-based chair that demonstrates how computational formwork and mycelium-based fabrication can converge to produce functional, low-impact furniture.