Add unsalted butter to a saucepan. Melt it over medium-low heat without stirring it (you want the components of water, fat, and milk solids to separate without disturbance). The butter will begin to boil and milk proteins will form a white layer on the surface (PHOTO 1). It’s actually the water in the butter that is boiling, not the butterfat. You want to continue to cook the butter until all of the water has gently boiled off. You’ll notice the boiling itself will calm down as the water content diminishes. Remove from the heat and use a spoon to skim off all the white milk solids floating on the surface, and discard (it’s easier to skim it without disturbing the layers once it’s no longer actively bubbling) (PHOTO 2). Now you can use the clarified butter, which is the pure butterfat. If you notice any white milky liquid on the bottom, that is residual water that hasn’t boiled off. Just use the yellow fat and stop once you hit the white watery residue at the bottom.