Chop the dark chocolate and place it in a bowl.
Heat the heavy cream until it just begins to simmer.
Pour the hot cream over the chopped chocolate and let it sit for a minute.
Stir until the mixture is smooth and glossy.
Add the orange zest and juice, along with the vanilla and salt.
Cover the ganache and refrigerate until firm, about 2 hours.
Once firm, scoop out portions of the ganache and roll into balls.
Coat the truffles in cocoa powder or crushed nuts.
Place the finished truffles on a platter and chill until serving time.