Begin by soaking the soybeans in 2 litres of water for at least 12 hours or overnight to soften them. Once soaked, rub the soybeans between your hands to loosen their skins and split them. Aim to split as many beans as possible; a few whole beans and leftover skins are acceptable.

Place a colander in a sink or large bowl. Use your hands to agitate the water, causing the skins to float to the surface. Gently pour off the water and skins into the colander. Repeat this process with fresh water until most of the skins are removed.

Transfer the soybeans to a pressure cooker with 2 litres of water and cook for 12 minutes, ensuring they are tender but not mushy. Alternatively, boil the soybeans in a pot over medium-low heat for 45 minutes to 1 hour, skimming off any foam that forms. Avoid overcooking to prevent the beans from becoming too soft.

Drain the cooked soybeans and spread them on a tray lined with a clean kitchen towel. Spread them evenly and allow them to steam dry and cool completely. Once cool, place the soybeans in a large, clean bowl. Stir in the brown rice vinegar thoroughly, ensuring all beans are coated. Sprinkle the tempeh starter evenly over the soybeans and mix well to distribute it uniformly.

Prepare a gallon-sized ziplock bag. Spoon the prepared soybeans into the bag, pressing out all the air before sealing it. Lay the bag flat on a hard surface and use your hands to spread the soybeans into an even layer. To ensure uniformity, place a chopping board on top of the bag, move it gently, and press down lightly.

Using a toothpick, prick evenly spaced holes across the surface of the bag, approximately 1 inch (2.5 cm) apart. Carefully flip the bag over and repeat the pricking process on the other side.

Set up a wire rack in a warm, well-ventilated location. Slide the bag of soybeans onto the rack. Allow the beans to ferment for 12 to 48 hours, depending on the temperature of your environment. After 12 to 24 hours, you will notice white fuzz beginning to grow.

The tempeh is ready when the entire bag becomes a solid block, and the soybeans are fully enveloped in white mycelium. This typically takes 36 to 48 hours.

To remove the tempeh, use a knife to cut the ziplock bag carefully down the middle without slicing through the plastic, allowing you to reuse the bag. Gently extract the tempeh one half at a time.

Cut the tempeh into your preferred shapes. Store it in the refrigerator for up to 4 days. Be aware that the tempeh will continue fermenting in the fridge, slowly intensifying in flavor. Eventually, it will over-ferment and spoil.

If you’re not planning to use the tempeh immediately, freeze it for up to 3 months to maintain its quality and freshness.