Step 1

Preparation Pat pork dry and sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Heat oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then cook pork (in 2 batches if necessary) along with shallots, turning pork over once and stirring shallots occasionally, until pork is browned and shallots are golden brown and tender, about 5 minutes total. Transfer pork with tongs to a plate and add vinegar, sugar, and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper to shallots in skillet. Cook, stirring until sugar is dissolved and liquid is thickened slightly, about 1 minute. Reduce heat to moderate, then return pork along with any juices accumulated on plate to skillet and turn 2 or 3 times to coat with sauce. Cook, turning over once, until pork is just cooked through, about 3 minutes total. Transfer pork to a platter and boil sauce until thickened and syrupy, 1 to 2 minutes. Pour sauce over pork.

Step 2

Preparation Pat pork dry and sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper. Heat oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then cook pork (in 2 batches if necessary) along with shallots, turning pork over once and stirring shallots occasionally, until pork is browned and shallots are golden brown and tender, about 5 minutes total. Transfer pork with tongs to a plate and add vinegar, sugar, and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper to shallots in skillet. Cook, stirring until sugar is dissolved and liquid is thickened slightly, about 1 minute. Reduce heat to moderate, then return pork along with any juices accumulated on plate to skillet and turn 2 or 3 times to coat with sauce. Cook, turning over once, until pork is just cooked through, about 3 minutes total. Transfer pork to a platter and boil sauce until thickened and syrupy, 1 to 2 minutes. Pour sauce over pork.