Preheat your oven to 325°F (163°C). In a bowl, combine crushed chocolate sandwich cookies with melted unsalted butter until moistened. Press into the bottom of a greased 9-inch springform pan. Bake for 10 minutes, then let cool.

In a large mixing bowl, beat room-temperature cream cheese and granulated sugar until smooth. Gradually add cornstarch, then mix in eggs one at a time. Add sour cream, heavy cream, instant espresso powder, and vanilla extract without overmixing.

Pour the filling over the cooled crust. Wrap the pan in aluminum foil and place it in a larger baking dish filled with hot water. Bake for 50-55 minutes until edges are set but the center is slightly jiggly.

Turn off the oven and crack the door, letting it cool for 1 hour. Then cover and refrigerate for at least 6 hours, preferably overnight.

For the optional topping, whip together heavy whipping cream with powdered sugar and espresso until stiff peaks form. Spread or pipe atop the cheesecake.

Before serving, dust with cocoa powder or sprinkle chocolate shavings and coffee beans for a nice presentation. Serve with hot espresso or cappuccino.