Beat egg and egg yolks in bowl; add sugar replacement and sorbitol and beat until thick and creamy.
Combine milk and cornstarch in saucepan; stir to thoroughly mix.
Heat until mixture is about to boil and is slightly thickened.
Remove from heat and pour over egg mixture in a steady stream.
Beat thoroughly to blend.
Return mixture to saucepan, cook and stir over low heat until custard thickens.
Do not allow to boil.
Stir in melted chocolate and strong coffee.
Place hot saucepan in bowl over ice cubes, to speed the cooling process.
When cool to the touch, fold in whipped topping.
Chill and freeze.
As it hardens, push the sides of the mixture to the center.
When nearly set, scrape mixture into large mixing bowl.
Beat well.
Pack and freeze.