Put all the ingredients except the vanillin into a pot and boil until the mixture caramelizes. Try to see if it is ready, by letting a drop into cold water, it shouldn't dissolve but also it shouldn't harden too much. 

Remove from heat. Let it cool for 5 minutes, add the vanillin powder and stir constantly until it whitens and becomes vanilla fondant (it's better if you use a wooden spoon). 

When we say stir constantly, don't overdo it if you get tired, leave it for a while and carry on later but don't stop until it is completely white.