Put all the ingredients, except the vanilla sugar, in a 24 cm stainless steel saucepan.
Bring to a boil, then reduce the heat and simmer over low heat until all the liquid has evaporated.
The operation takes 30 to 45 minutes.
Do not try to increase the heat to speed up cooking, otherwise your peanuts will not be cooked enough.
The sugar will then crystallize and form like sand around the peanuts. Add the vanilla sugar then.

With a wooden spatula, stir the peanuts constantly to coat them well and continue to heat the mixture over medium heat (not too high to avoid burning them) until the sugar starts to caramelize around the peanuts (20 to 30 minutes).

When the peanuts are well caramelized, place them on a silicone mat.
As soon as they have cooled slightly, separate them from each other, then wait for them to be completely cold before storing them in an airtight box.