Preheat oven to 400ºF / 200ºC (if you have convection, turn it on!). Line two baking trays with parchment paper or silicone baking mats.
In the bowl of a stand mixer, cream together the butter, brown sugar and granulated sugar for about 2-3 minutes on medium with the paddle attachment until fluffy.
1 cup unsalted butter, ¾ cup dark brown sugar, ½ cup granulated sugar
Add eggs one at a time then stir in vanilla.
2 large eggs, 2 teaspoons vanilla extract
With mixer off, add in cocoa powder, cake flour, all-purpose flour, baking powder, baking soda, and salt.
½ cup unsweetened cocoa powder, 1 cup cake flour, 1 ½ cups all-purpose flour, 1 teaspoon baking soda, 1 teaspoon baking powder, 1 teaspoon kosher salt
Mix on low just until all dry ingredients are incorporated. Do not over mix.
Add in white chocolate and semi-sweet chocolate, stirring on low until evenly distributed throughout the batter.
Scoop out 2 ounce portions of dough and roll between your hands to form into a smooth ball.
Place about 2 inches apart on prepared sheet trays.
Bake for 5-6 minutes, rotate trays and bake another 5minutes until tops of cookies are just browned.
Allow to cool on trays for 15 minutes then transfer to cooling racks.
Dive in and enjoy the chocolatey goodness!