
Soft and chewy brown butter oatmeal cookies, filled with fluffy vanilla buttercream.
In a saucepan, melt the butter over medium heat. Continue to cook the butter, swirling the pan occasionally. When the butter starts to foam, and nutty golden brown solids have formed at the bottom of the pan, the butter is done. Scrape the browned butter, including all the browned bits, into a mixing bowl. Let cool at room temperature for 30 minutes.
Use an electric mixer to beat all the ingredients together until light and fluffy.