Melt one cup of butter in a small pot. I have done this with both salted and unsalted butter, choose wisely based on your intended use.

Melted butter over medium heat. Keep heating, the butter will begin to foam.

While the butter foams, I tend to swirl once or twice.

You can see the foam has gone (water has left the butter) and it is getting golden. Once you start to see the milk solids browning on the bottom swirl until deep in colour and then remove from heat and pour in a bowl to cool quickly.

Yummy, nutty, butter on the bottom. It looks burnt but that's just my crappy camera. Scrape all the good bits into a bowl and use where necessary.