Can anyone explain..

[User9574]

Lindt chocolate balls? Why are they cold inside? How does the chocolate melt so quickly?

C'est le magique de l'artisan de choco.

Something to do with the addition of coconut oil that tricks the body into thinking the chocolate is at a lower temperature than your mouth. The wonderful thing about chocolate is that it normally melts in the mouth so this trick makes it feel cooler.
Also magic as pp said.