01 - Preheat oven to 325°F. Grease a 9-inch springform pan and line the bottom with parchment paper.
02 - Pulse chocolate sandwich cookies in a food processor until fine crumbs form. Mix with melted butter until combined. Press firmly into the bottom of the prepared pan. Refrigerate while preparing the filling.
03 - In a large bowl, beat softened cream cheese and granulated sugar together until smooth and creamy.
04 - Add eggs one at a time to the cream cheese mixture, mixing well after each addition.
05 - Blend heavy cream, sweetened condensed milk, alcohol-free Irish cream syrup or substitute blend, vanilla extract, and cornstarch into the mixture. Mix just until smooth—do not overbeat.
06 - Pour filling over the prepared crust. Place the pan on a baking sheet. Bake for 55 to 65 minutes, or until the edges are set and the center jiggles slightly.
07 - Turn off the oven, crack the door open, and let the cheesecake cool inside for 1 hour.
08 - Remove from the oven and cool completely at room temperature. Refrigerate for at least 4 hours or overnight.
09 - Whip heavy whipping cream with powdered sugar and vanilla extract until stiff peaks form. Spread or pipe over the chilled cheesecake.
10 - Top with grated chocolate or cocoa powder if desired. Slice with a clean, sharp knife, wiping between cuts for neat slices.