Preheat oven to 350°F.
In one bowl, combine all cookie wet ingredients and mix until smooth. In a separate bowl, combine all cookie dry ingredients, then mix wet and dry together. Add mix-ins.
In another bowl, combine all brownie wet ingredients and mix. In a separate bowl, mix all brownie dry ingredients, then combine wet and dry.
Line a cookie sheet with parchment paper and lightly coat with cooking spray.
Spread the brownie batter evenly.
Drop spoonfuls of the cookie dough on top of the brownie layer.
Add chocolate chips or toppings (optional).
Bake at 350°F for about 15-20 minutes, or until edges are set but center is slightly soft (should be slightly underdone looking but toothpick will come out clean).
Remove from oven and allow to cool completely so it firms up.
Once cooled, slice into 88 pieces or desired size. Then enjoy!
