Grease and line a 20cm square baking tin with baking paper, leaving a little overhang for easy lifting later.
Crush the biscuits, either in a food processor or by sealing in a plastic bag and bashing with a rolling pin.
150 grams ginger snap biscuits, 100 grams digestive biscuits
In a large bowl combine the crushed biscuits with glace cherries and chopped pistachios. Mix well to combine and make sure cherries are dispersed, or they easily clump together.
150 grams ginger snap biscuits, 100 grams digestive biscuits, 200 grams glace cherries, 50 grams pistachios
In a small pan on medium-low heat (or in the microwave in short bursts) melt the butter, golden syrup and 100 grams/3.5oz of the white chocolate together until smooth. (you can also add the syrup from the glace cherries for optional extra sweetness).
115 grams butter, 3 tbsp golden syrup, 400 grams white chocolate
Spoon the mixture into the prepared tin and press down firmly with the back of a spoon or spatula to pack it in and create an even layer. Pop in the fridge while you prepare the topping.
Melt the remaining 300g white chocolate, then pour over the tiffin base and spread out evenly.
400 grams white chocolate
Chill in the fridge until fully set. Minimum 2 hours, ideally overnight.
Allow to come to room temperature then slice into 16 squares and enjoy.