Line an 8x8x3-inch tin with baking paper and set aside.
Melt the chocolate, butter and golden syrup together in a saucepan. Leave to cool for a minute or two.
Crush the digestive biscuits into medium-sized chunks then add them to a large bowl along with the Cornflakes and mini marshmallows. Mix to combine.
Pour the melted chocolate into the bowl and mix well until everything is evenly coated. Transfer it to your lined tin and press down firmly into place.
Refrigerate for 3 hours then cut into squares and enjoy!
Video
Notes
Store in an airtight container in the fridge for up to 2 weeks.