¼cupgranulated sugar(for rolling the cookie dough)
½cuppowdered sugar(for rolling the cookie dough)
Instructions
In a mixing bowl, whisk together the flour, cocoa, baking soda, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, combine the softened butter, granulated sugar, and light brown sugar. Mix until well combined, about 2 minutes. Add the eggs and egg yolk, one at a time, mixing after each addition. Mix in the vanilla.
With the mixer running, slowly add the flour mixture and mix until just combined.
Using a tablespoon cookie scoop, portion the dough on a parchment-lined baking sheet. Chill the sheet pan in the refrigerator for 30 minutes.
Preheat the oven to 375 degrees. Roll the chilled balls of cookie dough in the granulated sugar and then in the powdered sugar, making sure the dough is heavily covered with the powdered sugar. Bake for 8-9 minutes. The center of the cookies will look slightly underdone. Let cool on the baking sheet for 3-4 minutes before transferring to a cooling rack.
Store in an airtight container. The cookies will keep for 3-4 days.