In a heavy bottomed pan, add the butter and heat it on low- medium heat.
Let it start melting and heat until all the milk solids are melted away.
Swirl the pan or stir it gently with a spatula occasionally.
As the butter starts browning, it also starts foaming. It will be difficult to see if the butter is browned right and doesnt end up being burnt.
A burnt butter will be dark and bitter.
Take it off the heat when you start smelling toasty and nutty smell. Pour it into a glass/metal bowl and let it cool.
Once it reaches room temperature, let it chill in the refrigerator for 30 minutes to an hour.
There will be some milk solid bits, you can either strain it or use it as is. I like the specks of milk solids on my tart, it adds a bit of flavour and interesting look! :D