1/4 cup live active milk cultures, which is contained in most yogurt made with milk, check the label to be sure
Instructions
Bring the milk up to temperature
Pour the milk into the inner pot of the Instant Pot.
Turn on the sauté setting. Bring the milk to almost boiling, stirring it often, until the milk reaches 180 degrees F. when tested with an instant-read thermometer.
It will take 20-25 minutes for the milk to reach 180 degrees F. when using the sauté setting on the Instant Pot - I timed it! (This can vary from Instant Pot to Instant Pot, depending on which model it is, etc.)
Cool the milk back down
Remove the inner pot of the Instant Pot to a hot pad or cooling rack, stirring the milk often since this will help it cool down. Cool the milk to 110-115 degrees F. This will take about 30 minutes.
Use an instant-read thermometer to check the milk during the cooling-down process. This will take 15-20 minutes. Don't let the milk cool down below 110 degrees F!
If you want to speed up the process of cooling the milk, you can place the Instant Pot into a big bowl of ice water (aka ice bath). This cooling process will take about 15 minutes, surprisingly fast, if you ask me.
Inoculate the warm milk by adding the live yogurt cultures
Once the milk has cooled down to 110-115 degrees F, it’s time to inoculate the milk by stirring in the active yogurt cultures, aka the “starter yogurt.”
Place the starter yogurt into a small mixing bowl; add about 1/2 cup of the warm milk to the starter yogurt, whisking them together until smooth and incorporated.
Now pour the start yogurt mixture back into the pot of warm milk; whisk gently to combine.
Incubate the yogurt
Cover the Instant Pot with the lid, locking it into place. Set the Instant Pot in a cozy, draft-free spot on your kitchen counter to incubate for 8-10 hours.
Once you’ve reached the 8-10 hour mark, it’s time to check the yogurt. When you remove the Instant Pot lid, the yogurt should look pretty solid but will still be a big jiggly at the center if you move the Instant Pot around; there may be bubbles on top of the yogurt and this is fine.
Chill the yogurt
Carefully transfer the yogurt to a very large bowl that has an sealable lid. Place the yogurt into the fridge and chill for 6-8 hours.
At this point, you can check the thickness of the yogurt and determine if you want to strain the whey from the yogurt to thicken it further. Once the yogurt is fully chilled, it is thick and creamy but you may want to strain it to make Greek yogurt.