Line two baking sheets with parchment paper and set aside. If you're working with cold butter, go ahead and preheat your oven to 350℉. If you're using room temperature butter, hold off on preheating until you chill dough. *(see note)
In a separate bowl, whisk together all dry ingredients including flour, cocoa powder, baking soda, baking powder, and salt. Set aside.
Cream together butter and both sugars together in the bowl of a stand mixer with the paddle attachment or in a mixing bowl with a hand mixer until combined. Add eggs and vanilla extract, mixing just until everything is combined.
Add the flour mixture into the wet ingredients, mixing only until just incorporated. Be careful not to overmix the dough.
Using a 2-ounce cookie scoop, place up to 8 (slightly heaping) scoops of dough onto each prepared cookie sheet, evenly spaced apart.
Refrigerate the scooped cookie dough on the baking sheets for 40 minutes while preheating your oven to 350℉. If you worked with cold butter, skip this step. *(see note)
While cookies bake, prepare the chocolate fudge glaze topping. See below.
Bake for 14-16 minutes, until the cookies are fully set. At the halfway point of baking time, swap and rotate trays.
Transfer each cookie sheet to a wire rack and use the bottom of a drinking glass to immediately smash down each cookie so it is flat across the top. Let cookies cool completely on the tray. This will make it easier to work with the topping and ensure chewy brownie cookies long after they’re cool.