Line a 9″x 13″ or a 30cm x 20cm baking tin with parchment paper
Cut the Mars Bars and butter into small pieces and place in a bowl over a saucepan of simmering water
Put over low heat and stir until melted and well mixed, next add in the golden syrup and stir
Next, add the melted mixture to the Rice Krispies cereal in a large bowl.
Stir until ingredients are combined.
Spoon into the lined baking tin and press mixture with the back of a spoon/spatula to ensure the mixture is nice and even
Melt the milk chocolate over a saucepan of simmering water.
Pour over the cereal layer, and spread evenly with a knife
Melt the white chocolate and using a spoon, pour thin lines horizontally across your milk chocolate layer
Using a spoon, blend these lines into the milk chocolate layer until you have a nice swirly pattern forming
Allow set for 4-5 hrs and then slice into squares