• Preheat the oven to 325°F (165C/150C Fan) and prepare your baking tin. This should be greased and lined with parchment paper to make the brookies easy to remove.

Instructions for the Cookie Layer

• In a small bowl, mix together the flour, baking soda and salt. Set aside.
• In a large bowl, cream together the butter and sugars until light and fluffy. Add the egg and vanilla, beating until well combined. Add the flour mixture, sifting into the butter mixture and stir until incorporated. Then add the chocolate chips and fold through to distribute.
• Using a cookie scoop or spoon, dollop the mixture into your prepared baking dish and then spread into an even layer. Placing scoops of the dough across the pan will make it easier to spread out.

Instructions for Brownie Layer

• In a large bowl, whisk together the egg, oil, water and vanilla. Set aside.
• In a separate bowl, mix together the sugars, flour, cocoa powder and salt.
• Add the dry ingredients (the flour mixture) to the wet ingredients and stir this together. Be careful not to overmix or beat - stir only until combined.
• Pour over the cookie dough and spread out evenly. The mixture will be very thick.
• Place the baking tray into the middle of the oven, baking for 25 to 30 minutes, until the top appears firm. You're looking to judge that the centre is no longer liquidy though it will still be gooey. A toothpick inserted in the centre should come out with a few crumbs.
• Remove from the oven and allow to cool in the pan for at least an hour before removing and slicing.