Step 1

Preheat the oven to 160C or 140C fan. Grease a 28cm x 18cm slice tin and line with non-stick baking paper, overhanging the two long sides.

Step 2

Place broken biscuits into a food processor and process until roughly crushed. Add butter and process until evenly moistened. Starting from the shorter end of the tin, use the back of a spoon to gently press down on the biscuit crumbs to distribute and form a smooth, even base and refrigerate until needed.

Step 3

Combine condensed milk, 30g butter and golden syrup in a small saucepan and cook over medium-low heat, stirring constantly, for 8 mins, or until lightly golden.

Step 4

While still warm, spread caramel mix over the chilled biscuit base, smoothing gently, so no crumbs are dragged through (don't worry too much about it being smooth – it will smooth out once cooked). Bake for 10 mins.

Step 5

Cool completely, then pour over melted dark chocolate combined with vegetable oil (the oil helps it cut without cracks).

Step 6

Chill until set, then divide and slice in half widthways and divide this portion into 3 lengths, then cut each into 4 squares. Repeat for the other half.