For crust, lightly butter an 8- or 9-inch springform pan. In a small bowl combine crushed wafers and melted butter. Sprinkle half of the crumb mixture onto bottom of prepared pan; set aside.
In a small saucepan combine 1-1/2 cups of the chocolate pieces and 1/2 cup of the whipping cream. Cook and stir over low heat until chocolate is melted. Cool for 30 minutes.
Chill a medium bowl and beaters of an electric mixer. Beat remaining 1-1/2 cups whipping cream until soft peaks form (tips curl); fold into chocolate mixture.
In a large bowl beat cream cheese, sugar, 1/4 cup of the caramel ice cream topping, and the vanilla. Stir in remaining chocolate and 1/2 cup of the pecans.
Drop half of the chocolate mixture by spoonfuls into the prepared pan; spread carefully. Spoon the cheese mixture over top. Sprinkle with remaining crumbs. Top with remaining chocolate mixture.
Cover; freeze for 4 to 24 hours. Before serving, remove sides of pan. Let stand for 15 minutes. To serve, cut into wedges. Top with remaining 1/4 cup caramel topping and 1/4 cup pecans. Makes 12 servings.