01 - Preheat oven to 325°F (160°C). Grease and line a 9-inch (23 cm) springform pan.
02 - Pulse the ladyfinger biscuits in a food processor or crush with a rolling pin until fine. Combine with melted butter and instant espresso powder, mixing until moistened. Evenly press into the base of the prepared pan. Bake for 10 minutes; allow to cool completely.
03 - Dissolve granulated sugar and coffee liqueur (if using) in hot espresso. Cool to room temperature.
04 - Using an electric mixer, beat cream cheese, mascarpone, and granulated sugar until smooth. Add eggs one at a time, mixing thoroughly after each. Blend in cooled espresso, vanilla extract, flour, and salt until just combined.
05 - Lightly brush or drizzle half of the coffee soak evenly over the cooled crust.
06 - Pour the cheesecake batter over the soaked crust. Tap pan to remove air bubbles. Place pan in a water bath and bake for 60 minutes or until just set but slightly jiggly in the center.
07 - Switch off oven, prop door open, and allow cheesecake to cool inside for 1 hour. Then, remove and cool completely at room temperature.
08 - Once at room temperature, refrigerate for at least 4 hours or overnight to set completely.
09 - Whip heavy cream, powdered sugar, and vanilla extract with a whisk or electric mixer until stiff peaks form.
10 - Release chilled cheesecake from pan. If desired, brush or drizzle remaining coffee soak over the top. Spread whipped cream smoothly over the surface.
11 - Dust generously with unsweetened cocoa powder and garnish with chocolate shavings if using. Slice and serve well chilled.