Start with the chewy toffee crisp centre.

Line two 20 cm square baking trays with baking paper.

In a saucepan, gently melt the butter, soft brown sugar and golden syrup on a low heat.

Stir continuously until everything's melted and forms a smooth caramel, then take off the heat and leave to cool slightly for a few minutes.

Working quickly, so the caramel doesn't harden, gently stir in the toasted rice until it's all well coated.

Using the back of a spoon, press this mixture evenly into one of the lined trays, then freeze for an hour, until the mixture is frozen solid.

This step is crucial to create a distinct, firm layer that can be easily handled and inserted into brownie batter.

Now make the batter.

Heat the oven to 180C (160C fan)/350F/gas mark 4, and put a medium heavy-based saucepan on a medium heat.

Melt the butter slowly, stirring continuously, then turn down the heat to low, add the dark chocolate and keep stirring until it melts and the mix is smooth and glossy.

Take the pan off the heat, stir in the sugar and vanilla, then add the flour and baking powder, and stir until it resembles fine breadcrumbs, with no visible lumps of flour or sugar.

In a medium bowl, beat the eggs for 20-30 seconds, until light and frothy.

Using a large metal spoon, carefully fold the eggs through the chocolate mix, keeping in as much air as possible, to make a smooth batter.

Pour half the batter into the second lined tray, spreading it out evenly.

Carefully lift out the frozen toffee crisp layer and gently peel off the paper.

Place the toffee crisp directly on top of the brownie batter in the tray, then pour the remaining batter over the toffee crisp, ensuring it is completely covered and spreading it out evenly to the edges.

Bake for 35-40 minutes, until the edges are set and the centre has risen and started to crack (it may still look a bit soft and wobbly).

Leave to cool completely in the tray on a rack for one to two hours (cooling it completely is essential for the structure to set properly before adding the topping and slicing).

Next, prepare the topping.

Set a heatproof bowl over, but not touching, a pan of simmering water, add the milk chocolate and gently melt, stirring until smooth and glossy.

Pour the melted chocolate over the cooled brownie, spreading it out smoothly, then chill for at least an hour, until set.

Remove the brownie from the tray (use the baking paper to help you lift it out), cut into six even strips, then halve these to make 12 bars.