2. Heat the oil until very hot in a 4-quart casserole or a Dutch oven with a lid. Add half the pork pieces. Sear the outside of half the pork over high heat until brown, turning once. Remove and sear the remaining meat. Set aside.
3. Reheat the pan and oil, add the Seasonings. Stir-fry until fragrant, about 15 seconds, then add the Braising Mixture. Reduce the heat to low, cover, and let simmer for 20 minutes. Add the pork, bring the liquid to a boil, and reduce the heat to low. Let simmer, covered, for 35 to 40 minutes. Add the sweet potatoes, stir, cover, and continue cooking for about 25 minutes, or until the potatoes are tender. Serve the pork and potatoes atop a bed of blanched or steamed greens, with some of the braising mixture spooned on top and accompanied by steamed rice.
Matt Goulding, author of Rice, Noodle, Fish, spent three months exploring the food in different regions of Japan. "To find a person who's been cooking nothing but tempura for 80 years of their life, it's a pretty remarkable thing," he says.