Preheat oven to 325°F (163°C). Line a 9-inch springform pan with parchment paper in the bottom and grease the sides.

Mix together the vanilla wafer crumbs, melted salted butter, and 1.5 tbsp sugar until well combined. Press the mixture into the bottom of the prepared springform pan.

Bake the crust for 10 minutes, then set aside to cool completely.

To make the filling, in a large mixing bowl, combine the room temperature cream cheese, room temperature mascarpone cheese, and 0.25 cup granulated sugar. Mix on medium-low speed until just combined. Do not mix on high speed or overmix, as the mascarpone cheese can begin to separate. Set aside.

In a separate cold mixing bowl, add 1 cup cold heavy whipping cream, 0.5 cup powdered sugar, and vanilla extract. Whip on high speed until stiff peaks form.

Slowly fold the whipped cream into the mascarpone cheese mixture until fully incorporated. Set aside.

For the Kahlua mixture, combine the warm water and instant espresso powder in a small bowl. Add 1 cup Kahlua and stir to combine.

Dip the ladyfingers one at a time into the Kahlua mixture, just long enough to absorb some liquid but not become soggy. Arrange the dipped ladyfingers in a single layer over the cooled crust in the springform pan.

Evenly spread the mascarpone cheese filling over the layer of ladyfingers.

Cover the cheesecake and refrigerate to chill and firm for 5-6 hours, or preferably overnight. Store any remaining Kahlua mixture in the fridge for later use.

Once the cheesecake is firm, prepare the Kahlua whipped cream. In a large mixer bowl, add 1 cup cold heavy whipping cream, 0.25 cup of the remaining cold Kahlua mixture, and 10 tbsp powdered sugar. Whip on high speed until stiff peaks form.

Carefully remove the chilled cheesecake from the springform pan. Use an offset spatula to smooth the sides if needed.

Add the Kahlua whipped cream to the top of the cheesecake. You can simply spread it or pipe it using a star tip for decoration.

Sprinkle a little cocoa powder over the top of the cheesecake, if desired, just before serving.

Refrigerate the tiramisu cheesecake until ready to serve.