MIX baking crumbs and margarine. Reserve 1 Tbsp. crumbs for topping; press remaining onto bottom of foil-lined 9×5-inch loaf pan.
BEAT cream cheese, peanut butter, sugar and vanilla in medium bowl with mixer until well blended. Whisk in Cool Whip. Remove 1/2 cup; mix with melted chocolate in small bowl. Spoon half the remaining cream cheese mixture over crust; top with chocolate mixture. Cover with remaining plain cream cheese mixture.
FREEZE 4 hours or until firm. Invert dessert onto plate. Remove foil; invert dessert, crumb-side down, onto platter. Sprinkle with reserved crumb mixture.
Adapted from KraftCanada.com