Mix crushed cookies and melted butter. Pat into a 9 x 13 pan. Cook chocolate, milk, eggs and sugar over medium heat until thick (like the consistency of fudge). Allow to cool. Spread over cookie crumb mixture. Freeze completely. Spread with ice cream. Spread with whipped topping. Sprinkle with crushed Heath Bars. Freeze until firm. Cut into 20 squares. Serve immediately.
NOTE: A few years ago I ran across "Lite" Oreos. Used them, no problem. Also use Lite Evaported Milk, Skim Milk Ice-Cream and Lite Topping. Still the same great flavor!