Wash the black beans under cold water and drain. Place them in the Instant Pot liner and cover with the 3 cups water. Cover with the lid, set the valve to the SEAL position, and pressure cook on manual for 30 minutes.
Let the pressure release naturally for 20 minutes. Remove the lid and drain the beans.
Stovetop:
Soak the black beans in cold water overnight or for at least 8 hours.
The next day, drain the beans and place them in a large saucepan. Cover with about 5 cups water and bring to a boil over medium-high heat.
Let it boil for about 10 minutes, then lower the heat, cover and let simmer for about 50 minutes. Test the beans from time to time to make sure they are not under or overcooked.
Drain the beans.
Next:
Place a clean kitchen towel on a large baking sheet. Transfer the drained beans to the kitchen towel and spread into an even layer. Let the beans drain and dry for 20-25 minutes.
Place the black beans in a large bowl, add the white rice vinegar, and stir until all the beans are "coated" with the vinegar. Sprinkle the tempeh starter and mix until well dissolved.
Use a thin chopstick or skewer to prick small holes in a small freezer bag (I used a 7x8-inch bag) at about 1-inch intervals.
Transfer the beans to the bag and fold the rest of the bag over the beans to keep it tight. It's important that the beans are tightly packed.
If you haven't already, wash the liner of your Instant Pot. Place 1 cup of water in the bottom and top with the steam rack. Place the bag on the rack. Cover with the lid.
Press the Yogurt button 3 times to set it to “Less” mode. Set the timer for 24 hours.
After 24 hours, touch the bag of beans; it should now produce its own heat. If it's cold, set the Instant Pot on yogurt mode for another 10 hours. Let incubate for at least another 24 hours with the lid on.
After 48 hours, your tempeh should be ready! The beans should be bound together into a firm loaf.
You can now transfer to the refrigerator. It will keep for up to 7 days. Use like soybean tempeh: marinade, fry, bake, sautée, etc!
Notes
If you don't have an Instant Pot for the incubation: Place the tempeh bag on a baking sheet and put it in the oven for about 20 hours at 86°F (30°C). My oven can go to a low temperature, but if yours can't, just let the oven light on or use a dehydrator set at around 86°F. Be aware the incubation time can take longer if the temperature is too low.