Finely chop the dark chocolate and grate the orange zest, setting them aside in separate bowls. Line a baking tray with parchment paper.

In a medium saucepan, gently warm the cold heavy cream and grated orange zest over medium heat until it begins to simmer, about 5 minutes.

Remove the saucepan from heat, add the chopped dark chocolate to the warm cream, and let it sit for 2-3 minutes before stirring until combined and glossy.

Pour the ganache into a shallow dish, cover with plastic wrap, and refrigerate for at least 2 hours or until firm.

Scoop out portions of the ganache with a melon baller and roll them into smooth balls.

Roll each chocolate ball in chocolate sprinkles, pressing gently to adhere the coating.

Place the coated truffles on the baking tray and refrigerate for an additional 30 minutes to set up.