In a medium mixing bowl, combine the crushed chocolate wafers, sugar, and butter until thoroughly mixed. Press into the bottom and sides of a springform pan, reserving 1/4 cup of the mixture for topping.
For the filling:
In a large mixing bowl, combine the cream cheese, chocolate syrup and sweetened condensed milk. Set aside.
In a standing mixer fitted with the whisk attachment, whisk the whipping cream until soft peaks form. Fold in the chocolate mixture until no streaks remain.
Pour chocolate mixture into the springform pan and top with reserved crumb mixture. Cover with plastic wrap and foil, and freeze, 6 hours or overnight.
Remove from freezer 30 minutes prior to serving. Store leftovers in the freezer.