Our constant companion, Ngrams Viewer, shows"view
"THE HISTORY Of the RENOWNED Don QUIXOTE De la MANCHA" is one of the earliest places where "Proof of the pudding" is found, and it gives a date of 1719 for the book.
Wikipedia, however, says the book was "The Ingenious Gentleman Don Quixote of La Mancha " published in two volumes in 1605 and 1615.
The ngrams search I did ranged from 1600. Did the name of the book change when it was translated into English. Was it first translated in 1719? There are three cites found, HotRDQdlM, HotRDQdlM2 both dated 1719 and HotRDQdlM3 dated 1725. Were these three volumes, of three editions?
Was "Proof of the pudding" borrowed from Spanish?
I found this part of the show especially interesting, but as is common, when I learn something new. I get new questions. Proof has a different meaning when it comes to booze. Powder in alcohol/water will burn if the alcohol is at least 50% ethanol (by weight, IIRC), and the British navy used that as a test for accepting rations being purchased.