Melt butter over medium-low heat, stirring every 10–15 seconds. It will foam, turn golden and smell nutty (5–7 mins). Remove from heat immediately once brown bits form. Add chocolate and cocoa powder to hot butter, and mix until completely smooth and lump-free. Let it cool slightly.

Whisk eggs and sugar well. Whisk until sugar is mostly dissolved. This step gives the shiny, crinkly top.

Add brown butter chocolate mixture + vanilla. Mix smooth. Add dry ingredients, flour, and salt. Mix just until combined. Do not overmix.

Cream cold butter + sugars. Whisk until slightly creamy and fluffy. Add egg, egg yolk, and vanilla. Mix until fully incorporated.

Add flour, baking powder, baking soda, and salt. Mix gently until just combined. No overmixing. Fold in chocolate chips.

Chill dough 30–60 mins for better flavor & texture.

Add a layer of cookie dough to the base of the pan and gently press it down.

Pour the brownie batter evenly over the cookie layer.

If you like, add small pieces of cookie dough on top for that classic brookie look.

To bake, preheat the oven (fan oven) at 170C, and then bake for 10-15 mins or until the edges are done and top is still little soft.