Line a baking tin with parchment paper.

Put the biscuits into a zip lock bag and crush them roughly with a rolling pin (or mortar and pestle). Set aside.

In a thick bottomed saucepan, heat the chopped chocolate, butter, milk and golden syrup over medium-low heat, stirring until melted.

Add the powdered sugar and cocoa powder, stir until smooth. Remove from heat.

Now add the crushed biscuits, walnuts, orange zest and vanilla extract and stir well to combine.

Spoon the mixture into the lined baking tin. Press and even the surface with a spoon.

Refrigerate for 3-4 hours or until set. Cut into squares and enjoy!