Melt butter over low heat in a heavy skillet. I use my lowest simmer to avoid burning.
The melted butter will sputter gently as the moisture boils out of it, and the bubbles will change from large to fine and foamy.
Gently push aside the foam which forms on top to assess the status of the milk solids at the bottom.
As it cooks on low heat, the liquid at the bottom will slowly cook off,
causing a scum to form on the top and the milk solids to brown at the bottom.
Remove from the heat when the liquid at the bottom is gone and the milk solids appear golden brown.
Do not let it overcook to dark brown or the flavor may be adversely affected.
Let the ghee cool for a few minutes, then strain through cheesecloth into a container with a tight lid, leaving most of the solids in the pan.
(I put a piece of cheesecloth, folded over to four layers, into a funnel to control the flow of the ghee into the bottle.)
Cool it completely.
This makes about 1 1/2 cups of ghee.