1
Prepare the Tin. Butter a 20cm square tin and line it with baking parchment.
2
Melt Basic Ingredients. In a large saucepan, gently melt the butter, sugar, syrup, and cocoa over low heat until smooth.
3
Mix in Biscuits and Additions. Take the pan off the heat and stir in the crushed digestive biscuits until every piece is coated. Leave some pieces chunky, they are what stop it setting into a solid slab.
4
Melt the Chocolate. In a separate heatproof bowl, melt the milk and dark chocolates either in the microwave or over a pan of simmering water.
5
Combine Mixtures. Add half of the melted chocolate mixture to the saucepan and mix well.
6
Transfer to Tin. Pour the combined mixture into the prepared tin, pressing down firmly and smoothing the top.
7
Top with Remaining Chocolate. Spread the remaining melted chocolate over the top of the mixture in the tin.
8
Add a Salty Finish. Optionally, sprinkle a pinch of sea salt over the chocolate layer.
9
Chill and Set. Place in the refrigerator for at least 2 hours.
10
Cut and Serve. Once set, remove from the fridge, dust with icing sugar and cut into squares.