Preheat your oven to 325F and line baking sheets with parchment paper.
In a medium saucepan, melt the butter over medium heat. Continue to cook, stirring and swirling the pan occasionally, until the butter turns golden brown and has a nutty aroma. Remove from heat and let cool to room temperature in a separate bowl.
1/2 cup unsalted butter
To the brown butter add in the brown sugar and granulated sugar and whisk until well combined. Add the egg and vanilla extract, and whisk until smooth.
1/2 cup brown sugar, 1/4 cup granulated sugar, 1 large egg, 1 tablespoon vanilla extract
In a separate bowl, whisk together the flour, baking soda, and salt. Add dry ingredients to the wet ingredients, mixing until just combined.