Roast the hazelnuts in a fan oven for 15 minutes at 150°C.
Bring the water and sugar to a boil at 110°C.
Add the hot hazelnuts.
Stir sandy and then caramelize.
Add the fleur de sel, then cool to room temperature on a baking sheet.
When cold, blend in a Robot Coupe® until you obtain an old-fashioned praliné (large grains).