On sauté mode, add in your cut up bacon. Cook it for 2-3 minutes.
Add in butter and let it melt before adding in the onions. Sauté until the onions start to soften and add in the garlic. At the same time, be sure to scrape up any browned bits from the bacon early.
Next, add in your potatoes, stock, salt, and pepper. Mix, place the lid on, set the valve to sealing, and set your Instant Pot on manual for 5 minutes.
Natural pressure release for 5 minutes when done, before quick releasing.
When done, to thicken the soup with one of the two methods: ° whisk the flour into the milk and then carefully stir into the soup. Simmer until thickened. ° add in the milk, remove some (or all) of the soup, blend with a handheld blender, and combine it back into the Instant Pot.
Top off with some cheese and crispy bacon before serving.