Procter & Gamble is jealously proud of its Duncan Hines brand of homemade-style chocolate chip cookies. To guard the secret of its crispy-outside, chewy-inside baking technique, P & G patented it last June and then sued three rival food giants. The suits charged that the competitors have been using P & G's patented process to make "infringing cookies," and had spied at a sales presentation and at cookie plants, once even flying a plane over a facility under construction.
One of those companies, Frito-Lay, the maker of GrandMa's Rich'n Chewy, has now countersued P & G for trying to...