01 - Preheat the oven to 320°F. Line the base of a 9-inch springform pan with parchment paper.
02 - Combine the crushed biscuits, brown sugar, and melted butter in a bowl. Press the mixture firmly into the base of the pan. Chill while preparing the filling.
03 - In a large mixing bowl, beat the cream cheese and granulated sugar until smooth and creamy.
04 - Add the heavy cream, then beat in the eggs one at a time.
05 - Mix in the cornstarch, alcohol-free Irish cream syrup, vanilla extract, and salt until just combined. Do not overmix.
06 - Pour the filling over the prepared crust and smooth the top.
07 - Bake for 55–60 minutes, or until the center is set but still slightly wobbly. Turn off the oven, crack the door open, and let the cheesecake cool inside for 1 hour.
08 - Refrigerate the cheesecake for at least 3 hours, or overnight, before serving.
09 - For the optional topping, whip the cream with powdered sugar and Irish cream syrup until soft peaks form. Spread or pipe over the chilled cheesecake before serving.