Soak 1 cup of dried black beans overnight in the Instant Pot, rinsing at least twice during the soaking time.
Cook in the Instant Pot for 30 minutes (this should result in beans that are easily mashable).
Allow the pressure to come down naturally, which will take another 30 minutes.
Remove the cover of the Instant Pot and allow the beans to cool until you can touch the sides of the cooking pot.
Drain off and reserve most of the cooking liquid in a bowl.
Add about 1/4 cup of fat of your choice. (I used to use butter or lard, but now usually use ghee or coconut oil. With coconut oil, the beans will be vegan.)
IMPORTANT! Don't leave out the salt or the beans will taste quite flat. Start with 1 teaspoon of salt and add more to taste.
Turn on the Instant Pot on slow-cook if needed so that the fat will melt. Using a vegetable masher, mash the cooked beans until about 3/4 mashed. Add a little of the cooking liquid if the beans are too thick.
Adjust the salt and add more ghee or coconut oil if you like.