Whisk eggs and sugar

• In a bowl, whisk the eggs and sugar together until light and slightly fluffy.

Melt chocolate and butter

• Melt the dark chocolate and butter together over a double boiler or in the microwave.
• Mix until smooth and let cool slightly.
• Add to the egg mixture and mix well, then stir in the salt and vanilla extract.

Finish the brownie batter

• Sift in the flour and cocoa powder and gently mix until combined.
• Add the chocolate chips and mix until evenly incorporated.

Prepare the dry cookie ingredients

• In a bowl, sift the flour and baking soda together and set aside.

Beat butter with sugars

• In a separate bowl, beat the butter until it becomes lighter in color.
• Add the white sugar, brown sugar and salt and continue beating on medium speed until smooth and creamy.

Make the cookie dough

• Add the egg and beat on low speed until just combined.
• Gradually add the flour mixture and mix on low speed until a smooth dough forms.
• Add the chocolate chips and mix until evenly incorporated.

Layer the brookies

• Line a baking pan with parchment paper.
• Spread half of the brownie batter evenly over the bottom, then add spoonfuls of half of the cookie dough.
• Add the remaining brownie batter, followed by the remaining cookie dough, and gently spread each layer as evenly as possible.

Bake

• Bake at 180 °C until a toothpick comes out almost dry, with just a few small brownie crumbs attached.

Cool and slice

• Let the brookies cool completely before slicing; the center will continue to set as they cool.