First, set out a large heatproof bowl to have at the ready. Place Unsalted Butter (1 cup) chunks in a medium-large light-colored skillet. Melt the butter over medium heat, whisking occasionally. After 5-8 minutes, the butter will start foam and then brown. You’ll start to see brown specks on the bottom and it will have a nutty aroma. When finished the butter will be amber, golden brown and the specks will be brown. Be careful not to burn!
Once the butter is browned, pour into the bowl immediately and let cool for 5-10 minutes
Whisk the All-Purpose Flour (2 cup), Baking Soda (1 teaspoon), and Salt (1/2 teaspoon) together in a medium bowl.
Add the Granulated Sugar (3/4 cup) and Brown Sugar (3/4 cup) to the slightly cooled brown butter. Using a stand mixer with the paddle attachment or a hand mixer, beat the butter and sugar on medium-high speed until mostly combined – about 1 minute. Then beat in the Egg (1) and Vanilla Extract (2 teaspoon) until combined.
Add the dry ingredients and mix together on low speed, slowly working up to medium speed until combined. The dough will be thick and slightly greasy.
Roll the dough into balls – about 1 tablespoon of dough each. Due to the dough’s texture, you may need to kind of press them into balls versus rolling. Do the best you can. Press the tops of the balls with Granulated Sugar (to taste) or roll and cover completely.
Place the balls on a lined baking sheet or a few plates, cover with plastic wrap, and refrigerate for about 30-45 minutes to chill.
Preheat the oven to 350 degrees F (180 degrees C) and line baking sheets with parchment paper or silicone liners.
Line the baking sheets with the chilled balls – a few inches apart (sprinkles/sugar up). Bake for 12-13 minutes until lightly browned around the edges and just set.
Remove from the oven and allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.