Long Story Short: The lesson learned is to READ THE RECIPE RIGHT, DUMMY!
Less Short Story: The recipe in Baker’s Illustrated called for 2 cups — not 1 cup — of flour!
Even less Short Story: Even I knew something was wrong when I reached the point when I was supposed to shape the cookies by hand and the batter (too soupy to be called dough) was way too sticky for that. Then the cookies started spreading unacceptably as they baked. Uh Oh.
Happy Accident? Instead of the thick, chewy chocolate chip cookies I was going for, I got lacy, buttery, candy-like and actually quite tasty … something. Harriet liked them. I don’t *think she was just being polite. I’m going to try again. But first I have to buy more butter!