Turn the instant pot onto saute mode and add butter and chopped onion. Saute until the onion is tender, and add the minced garlic.
Add the cubed potatoes, the chicken broth, salt, and black pepper into the instant pot.
Close the lid, pressure cook for 8 minutes, and release the pressure.
In a separate bowl, whisk together half-and-half and flour.
Open the lid to the instant pot and mash the potatoes to your desired consistency. Add the half-and-half slurry, along with shredded cheese.
Turn the instant pot back to saute mode and cook for 1-2 minutes or until the soup begins to bubble.
Garnish the soup, serve, and enjoy!