Preheat the oven to 350 degrees. Line two baking sheets with parchment paper.
In a medium bowl, combine flour, cocoa powder, baking powder and salt. Then set aside the flour mixture.
1 ½ cups (188 g) all-purpose flour, spooned and leveled , ½ cup (40 g) Dutch process cocoa powder , ½ teaspoon salt, ½ teaspoon baking powder
In a large bowl cream the softened butter, brown sugar and granulated sugar together with an electric hand mixer on high speed until fluffy, about 2 minutes. (You can also use the bowl of a stand mixer fit with a paddle attachment.)
¾ cup (168 g) unsalted butter, softened, ¾ cup (165 g) light brown sugar, packed, ¼ cup (50 g) granulated white sugar
Add in the egg yolks and vanilla to the butter mixture and mix for one minute on medium speed until pale and fluffy.
2 egg yolks, at room temperature, 1 ½ teaspoon vanilla
Add in the dry ingredients and combine on low speed.
Scoop the dough into 17 portions with a large, 2 tablespoon cookie scoop, then roll into balls. Slightly flatten out each, then place a frozen ganache ball in the center. Then close the ganache ball in with the cookie dough and roll into a ball again. Make sure the ganache is completely covered in cookie dough.
Transfer the formed cookie dough to a prepared baking. Bake 6 cookies at a time for 10-11 minutes.
Let the cookies cool for 10 minutes on the cookie sheet, then transfer the baked cookies to a wire rack to cool for 5 minutes, or until cool enough to handle. Sprinkle with powdered sugar and serve!