In a large bowl whip the cream until stiff. ( set aside 1/2 cup of whipped cream for the topping).
In a medium bowl, beat the mascarpone, sugar, juice and zest until creamy. Fold the mascarpone mixture into the whipped cream until combined.
Spoon the mousse into 4 cups or glasses and chill for 1 hour. Top with a dollop of whipped cream, sprinkle with chopped white chocolate or lemon zest before serving if desired. Enjoy!
Notes
This is a great make ahead dessert as it will stay good for 2-4 days when stored properly. To store, cover each bowl or glass tightly with plastic wrap and refrigerate until ready to serve. Add any additional garnish right before serving and if you are serving a crowd you may want to double or triple the recipe based on the number of guests.