Double Chocolate Cookie Bars
["2 c. finely crushed, cream-filled chocolate sandwich cookies (24 cookies)", "1/4 c. margarine, melted", "2 c. (12 oz.) semi-sweet chocolate chips", "1 (14 oz.) can condensed milk", "1 tsp. vanilla extract", "1 c. chopped walnuts"]
["Combine crumbs and margarine; press firmly on bottom of a 13 x 9-inch baking pan."]
["cookies", "margarine", "semi-sweet chocolate chips", "condensed milk", "vanilla extract", "walnuts"]