Preheat your oven to 180°C (350°F) and prepare a greased 20cm-square cake tin lined with non-stick paper.

Melt together dark chocolate and unsalted butter in a medium saucepan over low heat, stirring until smooth.

Whisk together brown sugar, eggs, plain flour, and cocoa powder in a large mixing bowl. Mix in the cooled chocolate and butter.

Pour the brownie batter into the prepared cake tin and bake for 30-35 minutes, checking doneness with a toothpick.

Prepare the caramel crunch by cooking caster sugar and water over low heat until it turns golden amber.

Stir in single cream and puffed rice cereal into the caramel, ensuring uniform coating for crunch.

Spread the caramel crunch mixture over the cooled brownie base and let it set at room temperature.

For ganache, melt dark chocolate with single cream over low heat, stirring until smooth.

Pour ganache over the caramel crunch layer and let it set at room temperature for at least 3 hours.

Slice the brownies and serve, optionally with vanilla ice cream.