Ensure the butter is at room temperature before you begin. Place the oven rack in the centre of the oven and preheat to 180°C (fan). Press the perforated edges of the baking tin down so it is ready for use.

Stir the butter in a mixing bowl until soft, taking care not to aerate it. Add the brownie mix and 100 ml of water and blend on the lowest speed until combined. Continue mixing for another 1 minute on low speed until a smooth batter forms. Spread the batter evenly into the baking tin.

Place the tin on the rack in the centre of the preheated oven and bake the brownies for approximately 40 minutes. The brownies are ready when the top has a glossy finish, the centre has slightly sunk and the inside remains slightly moist. Allow the brownies to cool completely in the tin before removing them.