Place the hazelnuts on a silicone sheet and bake them in the oven for 15 mins at 160C.
Put the sugar and water in a pan and heat to 113C, slowly add the hazelnuts and stir them coating them in the caramel.
The sugar will crystallise around the hazelnuts, when this happens, spread them out on a silicone baking sheet and make sure they are all separate, you don’t want them to clump together.