Director Stephen Frears (High Fidelity) is not necessarily known for his Busby Berkeley touch. But in Mrs. Henderson Presents, he whips up a flaky musical pastry around Judi Dench's saucy Oscar-nominated performance as the moneybags widow who revitalized a wartime London theater by suggesting that the high-kickers take it all off. EXTRAS Mrs. Henderson's original dancers are charmingly unabashed in making-of interviews. Frears, meanwhile, admits in a commentary that he was ''very taken, reading the script, with the idea of Judi saying 'f---' at the end of it. My heart leapt.''