In a medium bowl, add the egg yolks. To do this, crack the large eggs and place the egg yolks in the medium bowl and place the egg whites in an airtight container. You can use them for other recipes.
In a medium saucepan, add the whole milk, heavy cream, sugar, and vanilla extract. Cook the mixture until the sugar dissolves over low heat. A candy thermometer is helpful here. Do not let the mixture get higher than 120 degrees.
With a ladle, scoop one scoop of the milk mixture into the eggs and mix well. When the milk is mixed well with the eggs, add the egg mixture into the rest of the cream mixture. Mix well until a smooth custard liquid forms.
Pour the mixture into a liquid measuring cup and set out 6 small mason jars. Pour mixture into the mason jars. Cover the mason jars with aluminum foil.
Add a cup of water to the Instant Pot and add the trivet. Place the mason jars into the Instant Pot. Close the Instant Pot and hit the manual button. Set the pressure to low pressure for 14 minutes of cook time.
Natural pressure release for 10 minutes. Remove the custard cups from the Instant Pot and let them cool to room temperature for at least 2 hours. At this point, you can refrigerate them to cool them off and to serve them cold.
Spoon sugar onto the top of the crème brulee and place them on a baking sheet. Broil them for 2 minutes or until the top of the custard cups are crispy and browned. Serve immediately.