1In 3-quart heavy saucepan, cook sugar and water over medium-low heat, stirring often, until sugar is dissolved. Increase heat to medium-high; boil gently, without stirring, about 8 minutes, until syrup turns a deep amber color, occasionally brushing down sides of pan with wet pastry brush and swirling pan. (Swirling the pan, instead of stirring, promotes more even cooking.) Gradually add whipping cream (sauce will bubble vigorously). Add 1/3 cup butter; stir gently until smooth. Remove from heat; stir in vanilla. Set aside.
2Heat oven to 325°F. In small bowl, mix cookie crumbs and 1/4 cup butter. Press crumbs in bottom of ungreased 9-inch springform pan. Bake 10 minutes. Cool completely.
3Spoon 1 pint dulce de leche ice cream into cooled crust; spread evenly. Drizzle 1/3 cup of the Caramel Sauce over ice cream; sprinkle with 3/4 cup of the pecans. Freeze 15 minutes or until ice cream is almost firm. Repeat layers with chocolate ice cream, another 1/3 cup Caramel Sauce and remaining 3/4 cup pecans. Freeze until almost firm. Top with remaining dulce de leche ice cream and another 1/3 cup Caramel Sauce. Cover; freeze 6 hours or up to 2 weeks. Refrigerate remaining 3/4 cup Caramel Sauce until serving time.
4Before serving, remove side and bottom of pan; place pie on serving plate. Top with whipped cream topping. In small microwavable bowl, microwave remaining Caramel Sauce uncovered on High 1 minute or until warm. Drizzle sauce over each serving.