Brownies:

1. In a bowl mix the melted butter with the white sugar, brown sugar and cocoa powder with a hand whisk or electric mixer until smooth.
2. Add the eggs and vanilla and mix again for a few moments to incorporate them.
3. Finish by adding the dry ingredients, flour, salt and chocolate chips and gently mix with a spatula to incorporate.
4. Pour the brownie batter into the square pan lined with parchment paper.
5. Spread the batter with an angled spatula and set aside.

Cookie dough:

1. In a bowl, mix the melted butter with the white sugar and brown sugar with an electric mixer for 1-2 minutes until smooth.
2. Add the egg and vanilla and mix again for 1 minute with a hand mixer.
3. Finish with the dry ingredients, flour, baking soda, baking powder, sea salt and chocolate chips.
4. Gently mix with a spatula until you have a smooth, soft batter.
5. Pour the cookie dough into the pan on top of the brownie batter.
6. Gently spread with an angled spatula until brownies are completely covered.

Baking:

1. Preheat the oven to 350°F / 180°C and bake the brookies for about 30-35 minutes until golden on top.
2. Check the cooking with a toothpick or the blade of a knife, it should come out with crumbs and not liquid batter.
3. Let the brookies cool completely in the pan before removing from the pan and placing on a large platter.
4. Cut the brookies with a large knife into 16 small equal pieces.