It's easy to overcook this, so be watchful towards the end of the cooking time. You want to bake this just enough and no more, to achieve the lovely fudgyness. Using a serrated plastic knife (a disposable one is fine) cut into 16 pieces; the plastic knife will cut cleanly, even when the brownies are still warm.
They're fighting over these in Nottinghill! - 11 Mar 2018