Preheat your oven to 160 degrees and line the base and sides of a 20cm square baking tin with baking paper.
Roughly chop the Caramilk chocolate and set aside until needed.
In a large saucepan (you want it to be big enough to accommodate the extra ingredients added later), melt the butter, cocoa and sugar over a low heat – stirring continuously.
Add the vanilla extract and eggs - whisking the mixture as you go.
Sift the flour over the mixture and whisk to combine.
Working quickly, add the most of the Caramilk pieces (leaving 1/4 aside) to your brownie mix and pour into your prepared baking tin.
Add the remaining Caramilk pieces to the top of the mixture and pop into the oven and bake for 35 minutes.
Allow Brownie to cool completely in the tin before removing and then cut into pieces to serve.