Melt the butter in a saucepan over medium heat. Continue to cook the butter, stirring occasionally until it turns a golden brown color and has a nutty aroma.
Remove from the heat, transfer to a small bowl, and let cool to room temperature. Once it has cooled, place in the fridge until it becomes solid again.
In a large bowl with a spatula or stand mixer with the paddle attachment, cream together the brown butter, sugar, and brown sugar until light and fluffy, or about 3–4 minutes.