Pour the chocolate into a heat-proof bowl and set aside. In a small saucepan over low heat, heat the cream and butter until hot and fully steaming, but not boiling. When steaming, pour the cream over the chocolate. Quickly stir together to ensure all of the chocolate is moistened, then gently shake the bowl so that all of the chocolate is submerged. Quickly cover the bowl tightly with plastic wrap or a lid to hold in the heat, and allow to sit undisturbed for 10 minutes.
After 10 minutes, uncover the bowl and whisk the mixture until smooth. Whisk in the vanilla and salt, then pour the ganache into a pan. Allow to cool to room temperature, then cover tightly with plastic wrap and refrigerate until firm and set, about 1 hour, depending on the depth of the ganache (a shallow layer will set more quickly than a deep one.)
Once set, remove the ganache from the refrigerator and allow to sit at room temperature for 20-30 minutes to soften. Scoop out about 1 tablespoon of ganache, mold into a ball with your fingers, then roll a few times between your palms to smooth slightly. Repeat until all of the ganache has been formed into truffles. Dust the truffles with cocoa powder, or roll in the toppings of your choice!
Enjoy right away, or store in the refrigerator in an airtight container for up to 2 weeks. Allow the truffles to sit at room temperature for 10-15 minutes before enjoying.