Using an electric mixer, beat the mascarpone cheese, melted chocolate, powdered sugar, and espresso powder in a large bowl until smooth and fluffy.
Divide half of the panettone cubes among 6 wine glasses or old-fashioned glasses. Sprinkle half of the liqueur over the panettone. Top with half of the mascarpone mixture. Repeat layering with the remaining panettone, liqueur, and mascarpone mixture. Sprinkle the chocolate shavings over the trifles and serve immediately. (The trifles can be prepared 1 day ahead. Cover and refrigerate. Let come to room temperature before serving.)