Preheat the oven to 350°F (175°C) and prepare a tart shell by pressing crushed cookies or pastry into a tart pan; bake for 10–12 minutes until lightly golden. Let it cool.
In a bowl, beat mascarpone cheese, powdered sugar, and vanilla extract until smooth and creamy.
Dip ladyfinger pieces briefly in strong coffee and layer them evenly in the tart shell.
Spread half of the mascarpone mixture over the soaked ladyfingers.
Repeat with another layer of coffee-dipped ladyfingers and the remaining mascarpone cream.
Chill the tart in the refrigerator for at least 2–3 hours to set.
Before serving, dust the top with cocoa powder and garnish with chocolate shavings if desired.