Light Custard Sauce

Directions

1. 1
   Gradually beat the sugar into the egg yolks and continue beating for 2 to 3 minutes until the mixture is pale yellow and forms the ribbon.
2. 2
   Beat in the optional starch.
3. 3
   While beating the yolk mixture, very gradually pour on the boiling milk in a thin stream of droplets so that the yolks are slowly warmed.
4. 4
   Pour the mixture into the saucepan and set over moderate heat, stirring slowly and continuously with a wooden spatula or spoon, and reaching all over the bottom and sides of the pan, until the sauce thickens just enough to coat the spoon with a light, creamy layer.
5. 5
   Do not let the custard come anywhere near the simmer.
6. 6
   Maximum temperature is 165 degrees on the candy thermometer (170 if you have used starch).
7. 7
   Then beat the sauce off heat for a minute or two to cool it.
8. 8
   Strain it through a fine sieve, and beat in one of the flavorings.
9. 9
   To serve hot: Keep the sauce over warm but not hot water.
10. 10
    If you wish, beat in 1 to 2 tablespoons of unsalted butter just before serving.
11. 11
    To serve cold: Set the saucepan in a pan of cold water, and stir frequently until cool.
12. 12
    Then cover and chill.