Making process:
(1) Boil milk on fire.
(2) egg yolks, cornstarch, sugar together and mix well. Pour with boiled milk and mix well.
(3) Pour (2) liquid into a thick-bottomed saucepan and continue to simmer over high heat, stirring slowly and constantly to prevent mush.
(4) Add salt to the pot when it opens, then simmer and stir for a minute or two to cook through.
(5) Remove from the heat and stir in the melted butter. To prevent the kestrel sauce from dehydrating and drying out during the cooling process, cover the surface with a layer of plastic wrap.
Precautions:
(1) To prevent the sauce from burning, reduce the heat to a simmer and keep stirring.
(2) The simmered custard should be cooled completely at room temperature before placing it in the refrigerator.