1. Combine sugar, cornstarch, salt and shaved/grated unsweetened chocolate to double boiler over simmering water. With whisk, stir ingredients till combined.
2. Add cold milk and while stirring constantly and cooking over boiling water, cook until thickened. Place lid on top of double boiler and cook 15 minutes longer.
3. In separate bowl, beat egg yolks and temper hot mixture into beaten egg yolks by adding about 1/4 cup of the hot mixture into the beaten eggs. Then add the tempered egg yolks back into remaining mixture in double boiler and cook for 2 minutes over hot (not boiling) water stirring constantly. Cool (not in fridge!) but on counter then add pure vanilla extract.
4. Pour into baked pie shell, cover with meringue if so desired and bake 15 minutes or until meringue is lightly browned. Otherwise once pie is cooled, you can keep it chilled in fridge and serve with whipped cream right before serving.
5. Add shavings of chocolate for that martha factor if you wish along with a sprig of fresh mint.