Instructions

1. 1
   Cover soybeans with water, and soak overnight or at least 12 hours.
2. 2
   Remove the hulls (i.e. skins) from the beans by rubbing between both hands (see notes).
3. 3
   Skim off most of the hulls either by washing them away or by using a skimmer or strainer. Some hulls may be left behind without affecting tempeh quality.
4. 4
   Cook beans until just tender, not mushy; undercooked is best for tempeh (see notes).
5. 5
   Drain beans, and spread to dry somewhere with airflow (see notes).
6. 6
   Collect beans into a bowl, and mix in the cider vinegar. This acidifies the beans slightly, inhibiting unwanted spoilage organisms during fermentation.
7. 7
   Sprinkle the tempeh starter over the beans and mix in well (see notes).
8. 8
   Pack the beans loosely into banana leaves, zip-lock bags, or shallow dishes for incubating. Zip-lock bags must be punctured at roughly 1 cm (½ inch) intervals to keep oxygen up to the fermenting beans.
9. 9
   Load the soon-to-be tempeh into your incubator, preferably on racks that will allow air circulation. An electric oven with a light on makes a pretty good incubator, because the light provides just enough heat to keep the beans warm while the fermentation starts happening.
10. 10
    Incubate for 12 hours or so at around 30–35°C (86–95°F) with a heat source (unless it's already that hot where you are).
11. 11
    After 12 hours, remove or turn off the heat source - the fermenting beans will be making their own heat, and may overheat if you keep them too warm.
12. 12
    Monitor periodically from then on, and remove when the beans are totally consumed by fluffy white tempeh with no gaps.
13. 13
    After fermentation is complete, serve straight away in your favourite tempeh recipe, refrigerate for two to three days, or freeze for up to two months.