Classic chocolate tiffin

Line a 20cm square cake tin with baking paper. Melt the chocolates, golden syrup, butter and cocoa together in a large heatproof bowl over a pan of simmering water, ensuring the bowl doesn't touch the water. Alternatively, melt in the microwave in 15-second bursts until smooth.

Fold in the crushed digestive biscuits and raisins until everything is coated. Spoon the mixture into the prepared tin and press down using the back of a spoon or a spatula until the surface is level and the mixture is firmly packed into the tin.

For the topping, melt the chocolates in separate bowls as before. Pour the milk chocolate over the tiffin, then smooth to the sides using a palette knife or spatula until completely coated. Drizzle over the white chocolate in a zig-zag pattern, then use a skewer to marble the white chocolate into the milk. Chill for at least 2 hrs until solid, then cut into squares to serve.