In a heavy-bottomed pan, melt the butter over very low to moderate heat. Continue to heat it until the butter stops popping and producing foam. If you let the milk solids caramelize it will turn into browned butter. Browned butter has a nutty flavor and doesn’t always pair well with certain dishes. Avoid this by keeping the heat low.
Remove the butter from the heat and use a spoon or a ladle to skim the milk solids from the surface. Be careful to not remove any of the golden butterfat underneath. Don’t stress if you can’t get it all. That’s what the next step is for.
Strain through a fine mesh sieve lined with a few layers of cheesecloth. This will catch any leftover milk solids. Pour into a jar and store.