Preheat your oven at 180c and line an 8x8 inch pan with parchment paper.
For the cookie -> In a small bowl, add your flour, baking soda and salt. Set this aside.
In a large bowl, add the melted butter, both sugars, egg and vanilla extract. Whisk everything until it's a smooth and fluffy mixture - about 2-3 minutes.
Fold in the dry ingredients and the chocolate chips, just until everything is incorporated.
For the brownie -> Brown the butter, by melting it in a pan and mixing it until it has lightly switched colour to brownish and releases a nutty aroma.
Add the cocoa powder in the butter, the olive oil, vanilla extract and chocolate chunks. Whisk until everything is a smooth mixture. (You can put the butter in the microwave for 2 minutes if it has cooled down and the chunks are not melting)
In a seperate bowl, add the eggs and sugars and whisk until the sugars are dissolved and it looks fluffier -> the sugar dissolving is very important, as that's what's giving us the cranky top.
Add the cooled brown butter mixture and mix until everything is smooth.
Lastly, fold in the flour and the chocolate chips.
Grab your prepared baking pan, and slowly start building your brookie, by adding half the mixture of the brownie, then scoop half of the cookie dough on top of it, add the rest of the brownie layer and the final part of the cookie dough.
Bake this for 45-55 minutes or until the edges are golden and the center is slightly fudgy.
Make sure to allow the brookie to cool down at least 2-4 hours before cutting and enjoying! ✨