Step 1

In a small saucepan, mix together condensed milk, golden syrup and 60g butter. Stir continuously over a gentle heat for 5 - 6 minutes until a thick caramel forms.

Step 2

Preheat oven to 180C. Grease a slice tin and line with baking paper, leaving extra hanging over the sides.

Step 3

Make the chocolate cake according to the packet instructions and pour into the prepared slice tin. Dollop spoonfuls of caramel on top of the cake batter. Use a metal skewer or small knife to swirl the caramel into the batter, being careful not to overmix. Bake for 20 - 25 minutes until the cake is just cooked through. Allow to cool.

Step 4

Place the dark chocolate and remaining butter in a bowl and microwave in 30-second bursts, stirring in between, until melted and smooth. Pour over cooled slice and spread out evenly. When the chocolate has set, slice into squares and serve.