Brookies

• unsalted butter↗120g/4½oz g

  softened, plus extra for the pan

• soft light brown sugar↗120g/4½oz g
• dark muscovado sugar↗100g/4oz g
• egg↗1 large

  plus 1 yolk

• plain flour↗250g/9oz g
• baking soda↗½ tsp tsp
• milk chocolate chips↗50g/2oz g
• unsalted butter↗185g/6½oz g
• dark chocolate↗185g/6½oz g

  (at least 70% cocoa)

• eggs↗3 large
• vanilla extract↗1 tsp tsp
• golden crystallized sugar↗275g/10oz g
• cocoa powder↗50g/2oz g
• plain flour↗130g/5oz g
• milk chocolate chips↗50g/2oz g

Step-by-step instructions

1. 1

   Grease a 23 cm square baking tin and line it with parchment paper. Preheat the oven to 180 °C (160 °C with convection/gas 4). First, make the cookie layer. Place the butter and both sugars in a bowl and whisk with an electric mixer until just combined (a hand‑mixer may be used). Add the whole egg and the yolk, whisk again until incorporated. Add the flour, ¼ tsp salt, baking soda and chocolate chunks. Press the cookie dough into the bottom of the prepared tin with the back of a spoon, then chill for 30 minutes.

2. 2

   For the brownie layer, melt the butter and chocolate in a heat‑proof bowl over a saucepan of barely simmering water, stirring until smooth and homogeneous. Let it cool slightly, about 10 minutes. Whisk the eggs, vanilla and sugar in a large bowl with an electric mixer until the mixture thickens slightly, about 3 minutes. Gently fold the cooled chocolate‑butter mixture into the whisked eggs with a large spoon until combined.

3. 3

   Combine the chocolate‑butter mixture with cocoa and flour, mixing well. Spread the brownie mixture over the cookie layer, distribute chocolate chunks and, if desired, sprinkle with sea‑salt crystals. Bake in the centre of the oven for 50 minutes to 1 hour, or until a skewer inserted in the centre comes out with a few crumbs. Allow to cool completely in the tin before cutting into squares.