There is growing interest in using living materials as sustainable alternatives to conventional materials in product design. Particularly, the ability of some species of mushroom to grow lightweight, rigid materials that can be moulded into complex 3D forms is of interest to a range of interactive applications including data physicalisation, aesthetic experiences of a space, and wearable computing. This tutorial aims to provide a hands-on experience with living, mushroom-based "myco-materials" that can be grown into a range of complex shapes, and introduce a cheap, low-technology workflow for the design and fabrication of 3D designs using living, sustainable materials.