Sago /ˈseɪɡoʊ/ is a starch extracted in the spongy center or pith, of various tropical palm stems, especially Metroxylon sagu. It is a major staple food for the lowland peoples of New Guinea and the Moluccas, where it is called saksak and sagu. A type of flour, called sago flour, is made from sago.
With a little further reading I found that you can substitute tapioca in recipes.. but if you want real sago.. gonna have to find an asian market or something. Apparently its hard to find.
This recipe comes from an undated cookbook featuring dairy products. The illustrations and introductory text suggest it is from the early 1950s. If sago was known then, what happened to it that it is not commonly known about today?
I believe that cornstarch can be used interchangeably. In fact, and maybe I dreamt this, there may have been a cornstarch branded “Sago” in times past. I have the clearest vision of the box, but again, I may have dreamed it.