Pour the heavy cream and coconut milk into the inner pot of an Instant Pot.
Place the lid on the pot and set it to sealing.
Press the yogurt button and adjust until it reads BOIL.
When the boil cycle is complete, use an instant-read thermometer to check the temperature. It should be 180° F. (This kills harmful bacteria.) If it isn't, set it to saute and heat until it is.
Once it is at least 180° F, fill a bowl with cold water.
Place the inner pot in the ice water bath and allow the mixture to cool until it reaches 110° F. (You can also allow it to cool at room temperature.)
Whisk in the yogurt.
Dry the bottom of the outside of the pot and return it to the Instant Pot base.
Place the lid in place and set it to sealing.
Press yogurt, and adjust the time to 8 hours.
After 8 hours, chill the yogurt for 8 hours.
Use a nut milk bag to strain the yogurt.