In a medium saucepan, combine the heavy cream and whole milk.
Heat the mixture over medium heat, stirring occasionally, until it begins to steam (but do not allow it to boil).
In a mixing bowl, whisk together the egg yolks and granulated sugar until the mixture is pale and smooth.
Slowly pour a third of the hot cream mixture into the egg yolks, whisking constantly to temper the eggs.
Return the egg yolk mixture to the saucepan and cook over medium heat, stirring continuously with a spatula.
Once the mixture thickens enough to coat the back of the spoon, remove from heat.
Chop the dark chocolate into small pieces and stir it into the custard until completely melted.
Add the fresh orange zest and stir to combine.
Let the mixture cool, then refrigerate it for at least 3–4 hours, or until completely chilled.
Pour the chilled mixture into an ice cream maker and churn according to the manufacturer’s instructions (about 20-30 minutes).
Transfer the ice cream to a container and freeze for 4-6 hours or until fully set.
Serve and enjoy!