HEAT sugar, morsels, butter, cream and corn syrup in small, heavy-duty saucepan over low heat, stirring constantly, until butter is melted and mixture is smooth. Remove from heat. Stir in vanilla extract. Cool until slightly warm.
DRIZZLE 1/3 cup chocolate mixture in bottom of crust; sprinkle with 1/4 cup nuts. Layer 1 pint ice cream, scooping thin slices with a large spoon; freeze for 1 hour. Repeat with 1/3 cup chocolate mixture, 1/4 cup nuts and remaining ice cream. Drizzle with remaining chocolate mixture; top with remaining nuts. Freeze for 2 hours or until firm. Top with whipped cream before serving.