In a medium bowl, mix the flour, black cocoa powder, baking soda, baking powder, and salt. Set aside.
1 1/3 cups All-purpose flour, 1/4 tsp Baking powder, 1/4 tsp Baking soda, 1/2 tsp Salt, 1/2 cup Black cocoa powder
Using a mixer in a separate bowl, add the melted butter, brown sugar, and sugar. Mix on high speed for 2 minutes.
1/2 cup Unsalted butter, 3/4 cup Brown sugar, 1/4 cup White granulated sugar
Add in the vanilla, egg, and egg yolk. Mix on medium speed until just combined.
1 tsp Pure vanilla extract, 1 Large egg, 1 Egg yolk
Add in the dry ingredients on low speed until just combined.
Preheat the oven to 350°F. Get out 2 cookie sheets and line them with parchment paper. Let the dough rest for 10 minutes before scooping.
Pour the sugar in a bowl. Use a small cookie scoop (1 oz or 1 Tablespoon) to scoop the dough. Roll each cookie dough in sugar. Place 12 cookie dough balls per cookie sheet.
1/3 cup White granulated sugar
Bake one cookie sheet at a time. Bake for 8-10 minutes.
Let the cookie sit on the hot pan for 5 minutes. Transfer to a cooling rack to cool completely.