1. In a medium bowl, combine the cream and the orange zest. Allow to sit for 30 minutes to infuse the flavors.
2. Melt the dark chocolate in a double boiler or in the microwave.
3. Whip the cream and orange infusion until soft and firm; add the melted chocolate slowly, folding in carefully.
4. Finely chop 4 of the Baci and fold into the mousse. Pour the mousse into 4 silicon molds; freeze for 1 hour.
5. Turn the mousse onto 4 plates; dust with cocoa powder and place remaining Baci on top. Makes 4 servings.