Put the butter in a pot and turn on medium heat to melt the butter, then reduce to medium-low to simmer.
As it heats up it'll form foam on the top that you can start to skim off, just keep an eye on it as it simmers and keep taking the foam off the top.
It will stop producing foam and quickly begin to change a more golden color with amber brown solids formed at the bottom of the pan. When you see this change and smell toffee flavors, it’s time to turn off the heat and remove the pan from the stove.
Now there are several stages you can stop it at, depending on how much of a nutty flavor you like. Obviously lighter brown on the bottom will be only slightly nutty in flavor, and the more you brown it, the stronger the flavor. Just depends on your preference.
Strain it through a cheesecloth.
Store in a glass mason jar.