Tempeh is the Indonesian name for a traditional fermented product made using the noble mould Rhizopus oligosporus (or Rhizopus oryzae). The tempeh spore is – much like koji or yeast – a starter culture that transforms whole pulses into a firm block. Unlike tofu, tempeh is not an import from China, but a unique, centuries-old invention from the Indonesian island of Java. There, it is still regarded today as one of the most important and nutritious staple foods. The oldest written mention of tempeh comes from the Javanese literary work *Serat Centhini* (whose stories are set in the 17th century). Tempeh was probably discovered by a happy accident when cooked soya beans were wrapped in banana or hibiscus leaves, on which the fungus grows naturally.

But why use tempeh spores for fermentation? As it grows, the fungus forms a dense, white network (mycelium) that binds the beans firmly together. At the same time, the fungus’s enzymes break down the hard-to-digest proteins and phytic acids in the soya beans. This makes the beans extremely easy to digest; they lose their typical ‘beany’ taste and instead develop a wonderfully nutty, mushroom-like flavour.