Grease and line a square 8 inch baking tin with parchment paper, ensuring two sides of the paper overhang. Put the butter and chocolate in a heatproof bowl and place on top of a medium saucepan that is filled with a small amount of water. You need to ensure the bottom of the bowl will not touch the water below. Place the saucepan on the stove on a medium heat and stir while the chocolate and butter melt. Once the mixture is lovely and smooth, remove the bowl from the heat and leave to cool slightly.

Preheat the oven to 320 F (160 C). Next, add the sugar and vanilla to the chocolate mixture and beat with an electric mixer until combined. Add the eggs, one at a time and beat again. Sift in the flour and stir until the mixture is smooth. Pour the brownie batter into your prepared tin and place in the oven. Bake the brownie for approximately 35-40 minutes. The brownie should have a nice cracked top and no longer wobble in the middle. Leave to cool completely.

To make the cookie dough, add the softened butter and sugars to a large mixing bowl and beat with an electric mixer until pale and creamy. Add the vanilla and beat again. Sift in the flour and add the milk and stir until a soft cookie dough forms. Add in your chocolate chips and sprinkles and stir through. Then place the cookie dough on top of your brownie and spread it out as evenly as possible.

Finally, melt your chocolate in the microwave, stirring in-between 20 second bursts, until just melted and pour oven the top. Add extra sprinkles. Pop into the fridge for 15 minutes to set, then cut and serve.