Preheat your oven to 350°F/177°C.
Line two baking trays with parchment paper or silicone.
In a microwave safe bowl, melt the unsalted butter.
Stir in your cocoa powders and set aside.
To the bowl of a stand mixer fitted with a whisk attachment (or large bowl if using a hand mixer) add your egg yolks and powdered sugar.
Whisk on high speed for 5 minutes until very thick and pale yellow in color.
Using a spatula, stir in your melted butter/cocoa powder mixture, salt, and vanilla extract.
Add your all-purpose flour and stir just until combined.
Scoop out your batter and drop your brownies onto your baking sheets.
Bake for 10-12 minutes for a 3 tablespoon scoop (9-10 mins for a 1.5 tablespoon scoop).
Let the cookies sit on sheet for 3-5 minutes before moving to a cooling rack.
