Place the trivet in the Instant Pot and fill with 5 cups of warm water. Turn on sauté mode and bring the water to a boil.
Crack the eggs and add them to a blender. Blend until smooth, about 15 seconds. Add the remaining ingredients to the blender and blend for 30 seconds, until full blended.
Pour the eggnog mixture into a 1.75 quart Pyrex bowl. Place the bowl on top of the trivet in the Instant Pot.
Whisk the eggnog continuously until the water returns to a boil and the mixture reaches 150° F. Then turn off sauté mode and leave Instant Pot on Keep Warm setting.
Continue to stir the eggnog until the temperature reaches 160° F.
Carefully lift the bowl out of the water and strain the eggnog through a cheesecloth-lined strainer into an airtight container. Chill overnight before serving.
Notes
Bring your eggs to room temperature before using. This will make it easier to make the custard mixture.
It's best to cool the eggnog overnight. But it needs at least 4 hours to chill before serving.
Use an instant-read digital thermometer to test the temperature of the mixture.