Combine pretzel crumbs, 1/2 cup sugar and butter; press onto bottom and 2 inches up side of 9-inch springform pan.
Reserve 2 tablespoons of the remaining sugar. Beat remaining sugar with cream cheese in large bowl with mixer until blended. Add liqueur; mix well. Add eggs, 1 at a time, mixing on low speed after each just until blended; pour into crust.
Bake 1 hour to 1 hour 5 minutes or until centre is almost set. Run knife around rim of pan to loosen cake; cool before removing rim. Refrigerate cheesecake 4 hours.
Spoon caramel sauce over cheesecake, spreading to within 2 inches of edge. Bring 1/4 cup whipping cream to boil in small saucepan. Remove from heat. Add chocolate chips; stir until melted. Let stand 10 minutes or until slightly thickened. Pour over cheesecake; spread to completely cover top.
Beat remaining cream in medium bowl with mixer on high speed until soft peaks form. Add reserved sugar; beat until stiff peaks form. Spoon into pastry bag fitted with star tip; use to pipe whipped cream onto cheesecake just before serving.