Oops, I should'a googled first. Interesting article inside...
From
http://www.jewishworldreview.com/0603/dictionary_men052903.asp
(As silly as using "receipt" to mean "recipe" may sound to our modern ears, your friend is absolutely correct. In fact, there was a time when the only possible definition of "receipt" was "a set of instructions for making something from particular ingredients."
English speakers used "receipt" with that meaning from the 14th century (the first recorded use of "receipt" is a reference to a medicinal preparation from Chaucer's Canterbury Tales, ca. 1386) until the 17th century, when it began to turn up in its now more familiar sense of "a written statement saying that money or goods have been received." (It also developed the senses of "receptacle" and "revenue office" before the 17th century, but these are now very rare.)
Interestingly, "receipt" predates "recipe," which first turned up in print in the 1500s, and which was also initially used to describe a formula for the preparation of medicine. Both words began to be applied to cooking instructions in the 18th century, after which "recipe" slowly became the preferred word, and "receipt" began to appear primarily in the context of "receiving something."
However, "receipt" can still be substituted for "recipe," and it has been featured in the works of such important writers as Charles D1ckens, Mark Twain, and Louisa May Alcott (and Shakespeare, of course).)
And from bartleby.com: (Rec`pe is Latin for take, and contracted into R (Rx?) is used in doctor's prescriptions.)
