Combine cookie crumbs and butter. Press firmly into bottom of ungreased 13 x 9-inch baking pan.
Whisk melted chocolate, sweetened condensed milk and vanilla in large bowl until well blended. Stir in nuts. Fold in whipped cream. Pour into prepared pan. Spread with whipped topping. Cover. Freeze 6 hours or until firm.
For Rocky Road Ice Cream Squares Variation: Substitute chopped peanuts for nuts. Add 1 cup miniature marshmallows. Proceed as above.
