Whisk the cornstarch with a few tablespoons of the milk to make a quick slurry. Set both milk and slurry aside.
Set the Instant Pot to sauté. Heat butter till beginning to bubble, then add mirepoix (carrots, onions, celery). Stir and cook for 5-8 minutes, until veggies are beginning to soften.Add garlic and thyme to Instant Pot, stirring to coat. Cook until fragrant, about a minute. Add milk, bone broth (or stock) and potatoes. Stir to incorporate.
Place lid on Instant Pot. Set to Manual/Pressure for 7 minutes, then do a quick release.* See note.
Remove lid and set Instant Pot to Sauté. Tip in slurry and heavy cream. Stir to combine. Allow to come to a simmer and simmer for about 5 minutes, until slightly thickened.
Scoop into bowls and top with desired toppings. Enjoy!
*To activate the quick release, you have to push a button. Be wary for your skin (steam burns!) and also for surrounding cabinetry. The excessive steam can damage paint or wood stains on cabinetry.
**Any potatoes should work for this. I used a mix of russet (4 small) and gold (3 large) potatoes for some textural interest. For russets, be sure to peel before dicing. With wax skin potatoes, you can keep the skin on. Be sure to thoroughly wash and remove any damage before dicing.