01 - Preheat oven to 325°F (160°C). Grease a 9-inch springform pan and line the base with parchment paper.
02 - In a food processor, pulse chocolate sandwich cookies until fine crumbs are achieved. Combine crumbs with melted butter until fully incorporated. Press this mixture firmly into the prepared springform pan. Refrigerate while preparing the filling.
03 - In a sizable mixing bowl, beat softened cream cheese and granulated sugar until the mixture is smooth and lump-free.
04 - Gradually incorporate eggs, adding one at a time and mixing thoroughly after each addition until just combined.
05 - Gently blend in the heavy cream, sweetened condensed milk, alcohol-free Irish cream syrup (or chosen substitute), vanilla extract, and cornstarch. Mix only until the batter is smooth; avoid overmixing.
06 - Carefully pour the prepared Irish cream filling over the chilled cookie crust in the springform pan.
07 - Position the springform pan on a baking sheet. Bake for 55 to 65 minutes, or until the edges are firm and the center exhibits a slight wobble when gently shaken.
08 - Turn off the oven, partially open the oven door, and allow the cheesecake to cool within the oven for 1 hour.
09 - Remove the cheesecake from the oven and allow it to cool completely at room temperature. Once cooled, refrigerate for a minimum of 4 hours, ideally overnight, to ensure proper setting.
10 - For the topping, whip heavy cream with powdered sugar and vanilla extract until stiff peaks develop. Spread or pipe this topping over the thoroughly chilled cheesecake. Garnish with grated chocolate or cocoa powder, if desired, before serving.
11 - For clean slices, use a sharp knife, wiping the blade clean between each cut.