Crush cookies and add softened butter. Pat mixture into 9x13 pan. Add softened ice cream and freeze. Warm hot fudge sauce slightly and pour over ice cream. Freeze again and then top with whipped topping and nuts if desired. Can be made in spring form pan with layers of ice cream, cookie mixture and sauce. After freezing, remove from pan and frost sides and top with whipped topping and decorate with additional piped whipped toppping and/or icings.
-from Darla Ouellette