Cook the butter at 130°C/265°F to give it a taste of hazelnut. Pour on a plate and let cool.

Emulsify the cold butter with the fleur de sel using a robot coupe or a hand blender. Save.

Bring the cream to a boil in a pan and save.

Bring the water and the sugar to the boil in a pan. Add the glucose and cook at a temperature of 185°C/365°F to obtain a nice caramel colour.

Stop the cooking of the caramel by slowly pouring the still warm boiled cream into the pan.

Re-cook at a temperature of 106°C/220°F and incorporate the emulsified butter. End by pouring the spread into the jars and close them tightly.