Step 1: Finely chop the dark chocolate and place it in a medium heatproof bowl. Ensure the pieces are small to help them melt evenly.
Step 2: In a small saucepan, gently heat the heavy cream over medium-low heat until it just begins to simmer around the edges. Do not bring it to a rolling boil.
Step 3: Pour the hot cream over the chopped chocolate in the bowl. Let it sit undisturbed for 5 minutes to allow the chocolate to soften.
Step 4: After 5 minutes, gently whisk the chocolate and cream together until the mixture is completely smooth and glossy. Stir in the fresh orange zest.
Step 5: Cover the bowl with plastic wrap and refrigerate the ganache for at least 2 hours, or until it is firm enough to scoop and roll. For best results, chill overnight.
Step 6: Once chilled, use a small cookie scoop or a teaspoon to portion out small amounts of ganache. Roll them quickly between your palms to form smooth, round truffles.
Step 7: Place the chocolate sprinkles in a shallow dish. Roll each truffle in the sprinkles until fully coated. Arrange the finished truffles on a parchment-lined tray.
Step 8: Store the truffles in an airtight container in the refrigerator for up to 2 weeks. Allow them to come to room temperature for 10-15 minutes before serving for optimal texture and flavor.