Grease and line a 9” square baking tin.
Break the 550g of Kinder chocolate into squares and microwave in 30 second bursts until completely melted. Set aside to cool.
Cut the butter into chunks and add to a saucepan with the golden syrup. Melt together over a low heat. Set aside to cool.
Whizz up the digestive biscuits in a food processor. Alternatively you can place them in a zip lock bag and bash them with a rolling pin until broken down into crumbs. Transfer the crushed biscuits into a large mixing bowl.
Chop your 150g of Schar Melto bars into chunks and add these to the biscuits, followed by the mini marshmallows and raisins/currants/cherries if adding. Mix everything together lightly with your hands.
Pour in the melted butter/syrup mixture, followed by the melted kinder chocolate. Mix with a wooden spoon until well combined.
Transfer the mixture to the lined baking tin and make sure it’s spread out evenly.
Push the extra chopped chunks/squares of Kinder chocolate and Schar Melto bar on top.
Refrigerate until completely set – about 4-5 hours.