In a microwavable safe bowl, melt the premium chocolate bar in 30 second increments. Stirring in between. Once melted, set aside to cool for just a bit.
In a medium bowl, sift the flour and cocoa powder. Add in baking powder and salt. Set aside.
Using a hand mixer, in a large beat the butter, brown sugar, and granulated sugar on high for about 2ish minutes. Add in the vanilla and melted chocolate. Continue beating on medium-high for 1-2ish minutes.
Add in eggs and egg yolk and continue mixing until combined. Add in the dry ingredients and mix on low until incorporated. Fold in the chocolate chips and chocolate chunks.
Preheat the oven to 350°F. Place cookie dough in the fridge to cool until the oven is done preheating. About 5ish minutes. The cookies need a short chill time. Line 2 cookie sheets with parchment paper.
Use a 3 Tablespoon cookie scoop, scoop the cookie dough balls onto the lined cookie sheets.
Bake the cookies for about 12-15 ish minutes. Right after they come out of the oven, top with additional chocolate chips and chocolate chunks. Let them cool for about 3-5 ish minutes before transferring to a cooling rack. Enjoy!