In a medium saucepan on medium heat. Bring the cream and vanilla to a boil (this is important, cold cream will stop the cooking and crystallized the caramel)
Set aside.
Place the glucose and sugar in a medium saucepan on high heat.
Bring it to a caramel stage (170C/340F) and whisk in (off the heat) the cream little by little.
Once fully incorporated, add the butter and Fleur de Sel, whisk until smooth.
That's pretty much it. Let it cool down and store.