Prepare an 8x8” pan with butter or oil and make a parchment sling or partial sling.
Use your stand mixer with the paddle attachment. Add butter and sugars into the bowl. Mix until thoroughly combined and fluffy. This is about 5 minutes on a speed 4.
Add the egg and mix until incorporated. Then add in vanilla extract and mix thoroughly.
In a second medium to large bowl whisk flour, baking soda, baking powder, and salt.
Slowly add the dry ingredients into the wet ingredients with the mixer turned onto low/medium speed.
Once well mixed, fold in 1 cup of chocolate chips, leaving behind about ¼ cup for topping the dough.
Cover and place in the freezer while you make the brownie batter. If you’re leaving it for more than 30 minutes, place it in the fridge instead.
Brownie Layer
Preheat your oven to 350° F.
Prepare a 9x9” pan with butter or oil and make a parchment sling.
In your stand mixer with the whisk attachment combine butter, oil, and sugars to cream, about 4 minutes on a speed of 4.
Add in one egg at a time, each should incorporate before adding another. Add in vanilla and mix.
In a separate large bowl sift in the flour, cocoa, and salt. Mix well.
Pour dry ingredients slowly into the wet ingredients slowly. Mix until just combined. Be sure to not over mix.
Pour batter into the prepared pan. Using a rubber spatula or offset spatula, smooth across the entire pan.
Assembling
Place both batter and cookie dough on the counter. Gently remove your cookie dough from its pan. And flip your chilled cookie dough into your brownie batter pan. Do not push it into the batter too far.
To get those puddles of chocolate on top of your brookies, add chopped pieces of chocolate (or chocolate chips) on top of the cookie dough. Gently pushing them in slightly into the dough.
Cover the top of the pan with foil, folding over the edges. Now you’re ready to put it into oven.
Baking
Place in the oven and bake covered for 30 minutes. Remove the foil and bake uncovered 15-20 minutes. Keep checking for doneness.
Take out of the oven and let sit and cool for 15-20 minutes. Also, you can add flakey salt on top.
Remove the clips and pull the sling out gently, placing brookies on a cutting board. Slice and serve.
Notes
Reheating: In the days after baking, be sure to heat those cookies before eating, maybe just 10 seconds in the microwave before you eat so they are nice and gooey!Stand Mixer/By Hand: You can make these without a stand mixer. You want to whip it to the point where they cream together, so you may need to double your whipping time. This is just the faster or easier way to do it. For the wet ingredients use a whisk (or handheld mixer) to mix. You can also use a wooden spoon for mixing wet and dry together.Sift: You really don’t always need to sift your flour or cocoa powder unless you have large lumps, then be sure you do so to remove any odd clumping.Prepare your pan: Be sure you prep your pan for easy removal. You can do a few different methods for this; my favorite is the parchment sling. Take two long pieces of parchment paper, cut the width of the base of your pan. The length should run over the sides. And then cut one on the perpendicular side. Grease your pan and add in the two sheets overlapping. Use metal binder clips to pin down each side (has to be completely metal, not plastic). This works great on square pans, but not always necessary for two pieces on a rectangle pan. You can also just grease your pan well.