In a small bowl, combine crumbs and melted butter. Set aside 1/2 cup; press remaining crumbs into a 15x10x1-in. pan. Slice bananas widthwise and layer over crust. Cut ice cream widthwise into 10 slices; place over bananas. Spread edges of ice cream slices to cover bananas and form a smooth layer. Sprinkle with nuts. Cover and freeze until firm.
In a large saucepan, melt chocolate chips and butter; stir until smooth. Pour over ice cream and nuts; freeze until firm.
In a large bowl, whip cream until stiff peaks form; spread over chocolate layer. Top with reserved crumbs. Store in freezer (will keep for several weeks). Remove from freezer about 10 minutes before serving.