Line baking sheets with parchment paper.

Vigorously whisk together the flour, baking soda, and baking powder and set aside.

Mix together the brown sugar and white sugar dredging mixture in another bowl and set aside.

Slice 10 tablespoons of the butter into tablespoon-sized chunks. Place in a thick-bottomed skillet over medium heat. The butter will foam a bit before subsiding. Once the butter takes on a tan color and begins to smell nutty take it off of the heat. Add the other 2 tablespoons of butter and mix it in until it melts.

Pour the brown butter into a mixing bowl fitted with a paddle attachment. Add the brown sugar and salt and mix. Add the egg, egg yolk, and vanilla extract and mix together, scraping down the sides and bottom of the bowl at least once.

Add the flour mixture in three increments being sure to scrape down the sides and bottom once or twice. Mix just until the flour is incorporated. The dough will be very thick.

Take ½ to 1 tablespoon-sized pieces of dough and gently roll them into ball shapes. Dredge them in the sugar dredging mixture until well-coated. Place on the baking sheet and sprinkle with a little bit of the sprinkling salt.

Bake for 10 to 12 minutes or until the edges have browned a bit. Be careful not to over-bake.

Allow to cool on the sheet for one minute before transferring to a wire rack to cool completely.