Preheat the oven to 350°F/180°C.
In a stainless sauce pan, bring the milk, cream, triple sec, vanilla extract and orange zest to a boil. When the milk mixture has boiled, remove it from the heat.
Add the chocolate and stir until melted and smooth.
Combine the egg yolks and sugar in bowl and whisk until pale yellow.
In 1 Tbsp. increments, add 3 Tbsp. of the chocolate mixture to the egg mixture, stirring between additions. Whisk the egg mixture into the chocolate mixture.
Divide the pudding evenly among four ramekins.
Place the ramekins in a baking dish and add enough water to the dish to reach half way up the sides of the ramekins.
Cover the baking dish with aluminum foil and bake until custard is set, about 30 minutes.
Remove the ramekins from the baking dish and refrigerate, uncovered, until cool.
When the pots de crème have cooled, cover with plastic wrap and refrigerate until cold, about 6 hours.
Serve with a dollop softly whipped cream and a dusting of cocoa.