Prep your tools. Line the bottom and sides of a 9×9-inch baking pan with parchment paper. Preheat the oven to 350F.
For the Chocolate Chip Cookie Dough Layer
- In a medium bowl, mix together flour, salt, and baking soda. In a large bowl, beat together softened butter with both types of sugar until light and fluffy. Add egg and vanilla extract, and beat again.
- Add dry ingredients to wet ingredients and form cookie dough. Add chocolate chips and mix again. Press the dough into the bottom of the prepared baking pan.
For the Oreo Layer
- Spread the Oreos over the cookie dough layer. Breaking some cookies to fit as needed.
For the Brownie Layer
- In a medium bowl, mix the cocoa powder with flour, salt, and baking powder.
- In a separate bowl, beat together softened butter with both types of sugars, then add eggs and vanilla extract, and mix well. Sift dry ingredients into wet ingredients, and mix well.
- Spread the brownie batter over the Oreo layer.
- Bake for about 40-45 minutes until the toothpick comes out almost clean.
- Let it cool completely for a couple of hours.