Set your Instant Pot to "Sauté" mode and melt the butter. Add the diced onion and cook for 3-4 minutes until softened, then add the garlic and cook for another minute.
Add the cubed potatoes, chicken broth, salt, and pepper to the pot. Stir to combine.
Close the lid, set the valve to "Sealing," and cook on high pressure for 8 minutes.
When the timer goes off, do a quick release by carefully turning the valve to "Venting."
Open the lid and use a potato masher to mash about half of the potatoes, leaving some chunks for texture.
Stir in the heavy cream and shredded cheddar cheese until melted and creamy.
Serve hot topped with crumbled bacon, sour cream, green onions, and extra cheese. Enjoy!