Preheat oven to 325 degrees F. Finely crush cookies and mix with 3 Tbsp. butter; press onto bottom of pie plate. Bake 10 min.
Meanwhile, in a small saucepan cook and stir unsweetened chocolate over low heat until melted. Remove from heat; cool.
In a medium mixing bowl beat sugar and butter with an electric mixer on medium speed about 4 minutes or until light and fluffy. Beat in melted chocolate and vanilla. Gradually add egg, 1/4 cup at a time, beating on high speed after each addition and scraping sides of bowl constantly. Spoon chocolate mixture onto cookie crust, spreading evenly. Cover and chill for 5 to 24 hours.
Mix 1/4 cup crushed cookies with half of the White Chocolate Topping and spread over top of pie; freeze for 15 minutes. Spread the other half of the White Chocolate Topping on top; freeze for 20 minutes. Finish by sprinkling crushed cookies on top of pie.
White Chocolate Topping
Melt chopped white baking bar with 1/4 cup whipping cream; cool. Beat 3/4 cup whipping cream in small mixing bowl with an electric mixer on low speed until soft peaks form (tips curl). Add baking bar mixture. Continue beating on low speed just until stiff peaks form (tips stand straight).