Preheat oven to 180 degrees (160 if using fan-forced). Grease and line a 20 X 28cm rectangular slice tray with baking paper and set aside.
Place butter and dark chocolate into a microwave-safe bowl. Melt in 30 second bursts, on 50% power, for approximately 3 minutes, stirring each time.
Add the vanilla extract and caster sugar to the bowl.
Sift over the plain flour and cocoa powder.
Add the beaten eggs. Fold through until just combined.
Very gently fold through the frozen raspberries and white chocolate chunks.
Bake in the oven for 30 minutes or until cooked when tested with a skewer. Allow to cool completely.
Place the store-bought frosting into a bowl. Add 1 drop of pink food colouring and stir until a smooth pale pink colour is achieved.
Spread the frosting over the cooled brownies.
Add extra drops of pink food colouring all over the frosting and swirl with a skewer.
Place into the fridge to set (the frosting will remain slightly soft).
Cut into slices and decorate with the extra raspberries and white chocolate.