In a mixing bowl, combine graham cracker crumbs, melted unsalted butter, and optional sugar until well mixed. Press firmly into the bottom of a 9-inch springform pan to form an even layer. Chill for at least 30 minutes.

In a large bowl, whip heavy cream using an electric mixer until stiff peaks form, about 3 to 5 minutes. In a separate bowl, beat the mascarpone cheese with powdered sugar and vanilla extract until smooth and creamy. Gently fold the whipped cream into the mascarpone mixture.

Brew a strong cup of coffee and let it cool. Dip ladyfingers into the coffee mixture quickly, then lay over the crust in a single layer. Spread half of the mascarpone filling over the top.

Add another layer of dipped ladyfingers and spread the remaining mascarpone filling over this layer. Cover with plastic wrap.

Chill in the refrigerator for a minimum of 4 hours, preferably overnight.

Dust the top with cocoa powder before serving. Slice and enjoy!