Preheat oven to 180°C. Line a pie tin with baking paper.
Place butter and brownie mix in a medium pot on medium heat. Stir continuously, until combined and all butter has melted. Remove from heat.
In a large bowl, whisk eggs with electric beaters on high for about 3 minutes, until pale and fluffy. Alternatively, whisk by hand.
Unroll pastry on a clean flat surface and remove paper. Lay into prepared tin and press into sides. Trim any overhanging edges as needed. Poke holes in the base of pastry with a fork.
Pour brownie mix into eggs and whisk quickly to combine. Fold through flour and then pour into pie tin.
Bake for about 45 minutes, until brownie is no longer jiggly in the middle and pastry is golden. Allow to cool before slicing.