01 - Line a baking sheet with parchment paper.
02 - Place dark chocolate and coconut oil in a heatproof bowl. Melt over a saucepan of barely simmering water using the double boiler method, stirring until smooth. Alternatively, melt in short bursts in the microwave, stirring frequently.
03 - Stir chopped hazelnuts and puffed rice cereal into melted chocolate, ensuring everything is well coated.
04 - Drop heaping tablespoons of mixture onto prepared baking sheet, forming clusters.
05 - Sprinkle a pinch of flaky sea salt on top of each cluster if desired.
06 - Refrigerate clusters for 30 minutes or until fully set.
07 - Once firm, transfer to an airtight container. Store in a cool place or refrigerate.