1. In a mixing bowl, whisk the heavy cream until stiff peaks form.
2. In another bowl, mix the mascarpone cheese, sugar, and vanilla extract until smooth.
3. Gently fold the whipped cream into the mascarpone mixture.
4. Combine the coffee and coffee liqueur (if using) in a shallow dish.
5. Dip each ladyfinger into the coffee mixture for a few seconds, ensuring they are soaked but not soggy.
6. Layer the soaked ladyfingers in the bottom of the trifle dish.
7. Spread a layer of the mascarpone mixture over the ladyfingers.
8. Repeat the layers until all ingredients are used, ending with a layer of the mascarpone mixture.
9. Dust the top with cocoa powder.
10. Refrigerate for at least 2 hours before serving.