Preheat oven to 350F. Line a cookie sheet with parchment paper and set aside.
In a large bowl, whisk 1 cup flour, ⅓ cup cocoa powder, ¼ tsp baking soda, ¼ tsp baking powder and a pinch of salt until incorporated. Set aside.
Using an electric handheld mixer or a stand mixer fitted with the paddle attachment, beat ½ cup butter, ¾ cup brown sugar, 1 egg and 1 tsp vanilla extract until combined. The mixture will look a little grainy and that's OK.
Pour your flour mixture into your butter mixture and gently stir until combined. Fold your chocolate chunks until evenly distributed.
Scoop a heaping tablespoon of cookie batter and place on your prepared cookie sheet, making sure there's at least 1-2 inches of space around each cookie. Take a piece of chocolate chunk and place it on top of each cookie while slightly flattening your cookie (don't flatten too much because it will spread on its own).
Bake for 8-10 minutes or until just set (see note 1)
Cool your cookies on the cookie sheet until they are sturdy enough to move to a cooling rack to cool completely (see note 2).
It is better to under-bake than over-bake these cookies so check at about 6 minutes and decide. See the post for more tips.
Don't move the cookies from the cookie sheet too early - they will fall apart. Don't wait too long either though because they will continue cooking on the warm cookie sheet.
I used a 1.5 TBSP cookie scoop and ended up with 15 cookies.