Add the butter to the pot until melted. Add in sour cream (milk, creme fraiche, broth, etc.), milk, salt
, and garlic. Using either a potato masher or a hand mixer, begin to mash the potatoes and mix in the butter. I don’t like mine super-smooth, but you can beat them until smooth if you like them that way. It helps to give it a few minutes to let the flavors shine, especially the garlic.