To make the mousse, in a small saucepan stir the milk together with the granulated sugar and the espresso powder over medium heat until the milk is hot, but not boiling, and the sugar is dissolved.

Place the chocolate chips in a blender.

Pour the hot milk over the chips. Run the blender on high until combined, just a few seconds, then add the egg whites and run the blender on high until light, about 1 minute.

Transfer the mousse to 4 small serving cups. Cover with plastic wrap and refrigerate until firm, about 3 hours.

To make the mascarpone whipped cream, in the bowl of an electric mixer stir together the mascarpone and the orange juice until smooth.

Add the cream, confectioners' sugar, and orange zest.

Whip until the cream forms soft peaks, about 1 minute.

Spoon a dallop of whipped cream onto each mousse and serve.