"Theo Chocolate in Seattle is the only organic, fair-trade, beans-to-bar chocolate made in the United States. It’s exceptionally good, too, and I’m not just saying that because I’m a part owner! If you can’t find it for this recipe, substitute a 70 percent cacao dark chocolate you know and love."
— Tom Douglas
To make the candied zest, use a 5-hole citrus zester to remove the zest from the oranges in long, narrow strips. If you don’t have a zester, remove the zest in long strips with a vegetable peeler, scrape off any white pith from the underside of each strip, and then julienne each strip finely with a sharp knife. Bring a small saucepan ¾ full of water to a boil, add the zest strips, and boil for 1 minute. Drain the zest and set aside.
Add ½ cup of the sugar and ½ cup of the water to the same saucepan, place over medium-high heat, and cook, stirring occasionally, until the sugar dissolves. Add the blanched zest to the syrup, reduce the heat to a simmer, and cook until the zest is tender, about 5 minutes. Remove the pan from the heat and let the zest cool to room temperature in the syrup. Then drain the zest, reserving the candied zest and 1 tablespoon of the syrup. Set them aside separately. (The zest can be stored in an airtight container at room temperature and the syrup in an airtight container in the refrigerator. They will keep for up to 5 days.)
In a heatproof bowl, combine both chocolates, ¼ cup of the liqueur, and 3 tablespoons of the water. Place over (not touching) barely simmering water in a saucepan and heat, stirring occasionally, until the chocolate melts and the mixture is smooth. Remove the bowl from the heat and let the chocolate mixture cool slightly.
In a large bowl, whisk together the egg yolks until well combined. Using a rubber spatula, mix a small amount of the warm chocolate mixture into the yolks to temper them and prevent them from scrambling. Then add the remaining warm chocolate mixture to the egg yolks and mix with the spatula until smooth.
In a stand mixer fitted with the whisk attachment, or in a medium bowl with a handheld mixer, combine the egg whites and 2 tablespoons of the sugar and whip on high speed until soft peaks form. Using a hand whisk, whisk about ¼ of the whites into the chocolate mixture to lighten it. Then, using a rubber spatula, gently but thoroughly fold about 1/3 of the remaining whites into the chocolate mixture. Repeat with the remaining whites in 2 batches.
Rinse and dry the bowl and the whisk attachment or beaters used for beating the whites. Pour 1 cup of the cream into the bowl and whip on high speed until soft peaks form. Using the rubber spatula, fold the whipped cream, about 1/3 at a time, into the chocolate-egg white mixture, folding until the mixture is smooth and no white streaks are visible. Spoon the mousse into a glass serving bowl or individual serving dishes. Cover with plastic wrap and chill for at least 3 hours or up to overnight.
In the stand mixer fitted with the whisk attachment, or in a medium bowl with the handheld mixer, combine the rest of the cream, the tablespoon of liqueur, and the reserved 1 tablespoon syrup and whip on high speed until soft peaks form.
Spoon the orange cream into a pastry bag fitted with a ½-inch star tip and pipe it decoratively over the mousse. Alternatively, attractively spoon the orange cream directly over the mousse. Arrange the candied zest over the orange cream. Serve immediately.