Preheat the oven to 180°C (160 fan/ 350F/ Gas 4) and grease and line a 30 x 20cm baking tin.
Place the butter and sugars in a large saucepan and melt on a low heat, stirring often.
225 g Butter, 300 g Caster Sugar, 150 g Light Brown Sugar
Take off the heat and stir in the dark chocolate pieces until they have melted.
150 g Dark Chocolate
Beat in the eggs.
5 Eggs
Fold in the plain flour and cocoa powder. Allow the mixture to cool for 5 minutes.
110 g Plain Flour, 50 g Cocoa Powder
Mix in the frozen mint aero bubbles.
184 g Mint Aero Bubbles
Pour the brownie mixture into the prepared tin and bake for 30 minutes until just set. Cool in the tin.
Drizzle over the melted dark chocolate and scatter over the chopped mint Aero bubbles. Cut into bars when the topping has set.
100 g Dark Chocolate, 70 g Mint Aero Bubbles