In 1930, a dietitian who owned a tourist lodge was cooking and baking for her guests. Unfortunately, she ran out of the baker’s chocolate she needed for the chocolate cookies that were on the menu. She hurriedly substituted a chocolate bar — cut up into tiny pieces — assuming they would melt. They didn’t — they just softened, instead.
The mistake turned out all right for her in the end, and even brought her a lifetime supply of chocolate! http://www.baconbabble.com/index.php/2009/12/15/the-history-of-the-chocolate-chip-cookie/ -via the Presurfer