Place butter in small saucepan over medium-low heat. Swirl and melt completely. Butter will boil. Continue to swirl and cook until butter turns golden brown and brown bits start forming on bottom of pan. Once butter has a nutty scent and is deep golden brown, remove from heat and transfer to a heat proof bowl. Make sure you spoon out all little black bits from the saucepan. Let brown butter cool at least 15 minutes before using in a cookie recipe.