• Line a 20cm square baking tin with clingfilm or nonstick baking paper, making sure it overhangs the edges of the tin.
• Place the dark chocolate and milk chocolate for the tiffin in a heat proof bowl with the butter and golden syrup. Microwave in 30-second bursts, stirring with a wooden spoon inbetween. Allow to cool to room temperature.
  150 g Dark Chocolate, 150 g Milk Chocolate, 100 g Butter, 125 g Golden Syrup
• Place the crushed digestives and Maltesers in a large bowl and stir.
  150 g Maltesers, 250 g Digestives
• Pour the melted chocolate mixture over the crushed biscuits and Maltesers and mix to combine.
• Spoon the tiffin into a 20cm square baking tin, lined with clingfilm, and press down firmly with the back of a spoon. Place the tin in the fridge whilst you make the topping

For the topping

• Melt the dark chocolate and white chocolate in the microwave in two separate bowls. Add a few drops of vegetable oil to each bowl and mix in (this will prevent the topping from cracking when cut).
  100 g Dark Chocolate, 100 g White Chocolate, ¼ teaspoon Vegetable Oil
• Dollop spoons of the dark and white chocolate over the tiffin and use a skewer to create a marble effect.
• Scatter over the Maltesers reserved for the topping and press down lightly.
  150 g Maltesers
• Refrigerate for 2 hours before lifting the tiffin out of the tin (using the overhanging clingfilm) onto a chopping board and cutting into bars with a sharp knife.