Set Instant Pot to Sauté function and melt butter. Add onion and celery, and cook until soft, about 2-3 minutes, then add minced garlic and thyme and cook until fragrant, 30 seconds more.
Add chopped Russet potatoes, carrots and chicken broth and place the lid on the Instant Pot. Set to Pressure Cook on High and set time for 8 minutes. Once finished, turn the valve to quick release.
In a small bowl whisk together 2 tablespoons milk and cornstarch to make a slurry.
Once the steam has completely released and the pin has dropped on the lid, open the lid and set to Sauté function again. Pour in slurry, remaining 1 cup milk, and heavy cream and let boil for about 5 minutes, stirring constantly. Season with salt and pepper to taste.
Garnish with shredded cheddar, bacon, and chopped fresh chives before serving.
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Notes
Use Russet potatoes to make this soup creamy. Russet potatoes have a high starch content and are preferred when making creamy potato soup.
You can cook the chopped bacon in the Instant pot before making the soup. Once the bacon is cooked, transfer to a plate and later garnish the soup with it.
If you like your potato soup less chunky, you can use an immersion blender to slightly blend the potato chunks. Don't overdo it or the soup can become gluey.
The soup will continue to thicken as it cools.
This soup is great on its own, or serve with crusty bread to mop the bowl.
Make this soup vegetarian by omitting the bacon and swapping the chicken stock for vegetable stock.
To make this soup dairy-free substitute milk and heavy cream with almond milk, and omit the cheese topping.