Preheat the oven to 160°C (fan-assisted convection). Grease and line a 20cm square tin with baking paper.

Whisk the butter with the sugar (sachet 1), then whisk in the egg until the mixture is thick and creamy. Add the brownie mix (sachet 2) and stir to form a glossy batter.

Spread the batter evenly into the prepared tin and bake for about 15 minutes until cooked through but still fudgy inside. Set aside to cool in the tin.

To prepare the ganache topping, gently heat the cream in a saucepan until it just starts to bubble. Remove from the heat, pour over the chocolate and set aside for 1 min to heat it through. Gently mix to form a smooth and glossy ganache. Chill the ganache in the fridge until thickened but not firmly set (see Tip).

Spread the ganache on top of the cooled brownie and gently tap the sides of the tin to even out any imperfections. Decorate with candy sprinkles. Place in the fridge to set the ganache, then slice up and serve.

Tip: Make sure your ganache is thick and luscious but still pourable before layering it on top of your brownie. If it is too runny, it can run down the sides and may not be able to hold up the sprinkles.