Sterilize your equipment. Place the trivet in the bottom of the Instant Pot. Pour 2 cups cold water into the pot. Place a small Pyrex measuring cup, a silicone spatula and a heat resistant tablespoon in the pot. Close the lid, move the venting knob to sealed and use the Manual/Pressure Cook button for 3 minutes. Naturally release the steam.
Remove the tools from the pot and place on a rack to dry.
Pour half a gallon of organic whole milk into the pot.
Use the Yogurt button and select Boil to bring the milk to 180º. It will say BOIL on the display and will take 35-40 minutes. The vent position doesn't matter.
When your Instant Pot beeps, open the lid and check the temperature with a meat thermometer. You can skim off the skin of milk that has formed on the top and discard. If the milk is not at 180º or higher, stir and close the lid again. Use the Slow Cook button and select Less for another 15-30 minutes. Stir and check the temperature again. Repeat, if necessary.
Once your milk has come to 180º, remove the pot from the unit and place onto the trivet to cool down to 111º.
While the milk is cooling, place 2 tbsp. of plain greek yogurt into the glass measuring cup and set aside. Be sure your yogurt contains live active bacterial cultures.
Use the meat thermometer to check that the milk has cooled down. Once it has cooled down, take 1/2 cup of the milk and add it to the glass measuring cup with the yogurt starter and stir well. Pour the starter mixture into the pot and gently stir to combine with the silicone spatula.
Incubate the yogurt for 8-12 hours. Place the inner pot back into the Instant Pot and close the lid. Again, the venting position does not matter in this process. Select the Yogurt button and use Normal function to incubate for desired time. I chose 8 hours, but you can go as long as 12 hours. The longer the time, the tangier the yogurt. Note that your Instant Pot will start at 00:00 and count up in this function.
Once the yogurt has finished, remove the inner pot and place in the fridge for a few hours to stop the incubation. If you do not have room in the fridge, scoop the yogurt into smaller mason jars or plastic containers and place in the fridge.
Your plain yogurt is great with granola and fresh fruit, or you can make a simple fruit sauce to mix in by bringing 2 cups fresh or frozen fruit and 1/4-1/2 cup sugar to a boil on the stovetop. Boil gently until the fruit is cooked down into a sauce.
