Line a 20cm square baking pan with parchment paper.
In a microwave-safe bowl, Place the tiffin's dark and milk chocolate, butter and golden syrup and microwave for 30 seconds.
Allow to cool completely for about 10-20 minutes.
To crush the biscuits, put them in the food processor and blitz them until they crunch.
Place the crushed biscuits and Maltesers in a large bowl and stir.
In a mixing bowl, mix together crushed digestives biscuits and Maltesers and then pour over the chocolate mixture; mix well until combined.
Transfer the mixture to the baking pan, and press down firmly with the back of a measuring cup. Put in the fridge.
To make the topping
Microwave the dark and white chocolate in two separate bowls for 30 seconds to melt.
Now, Pour spoons of the dark and white chocolate over the tiffin and use a skewer to create a marble effect.
Scatter over the Maltesers and put the pan in the fridge again for 2-3 hours.
Cut the tiffin into bars.
Notes
Use a large, sharp knife to cut the Tiffin. Hold it for a while under hot, boiling water. This will ensure that you cut smoothly through the chocolate topping.
If the Malteser has become too hard to cut straight out of the fridge, allow it to come to room temperature by letting it sit for around 30 minutes.