Brew two cups of strong coffee, allowing it to reach room temperature; mix in coffee liqueur if desired and set aside.

In a large bowl, whip one cup of heavy cream with an electric mixer until soft peaks form, about 3 to 5 minutes.

In another bowl, combine 8 ounces of mascarpone cheese, ¼ cup of powdered sugar, and 1 teaspoon of vanilla extract; blend until smooth. Gently fold in whipped cream.

Quickly dip ladyfingers into the coffee mixture. Layer them in serving glasses, followed by the mascarpone mixture; repeat layers.

Smooth the top, dust with cocoa powder, and optionally sprinkle with grated dark chocolate; cover and refrigerate for at least 4 hours.