Cook pancetta in a large skillet over medium-high 3 minutes or until crisp. Remove pancetta, reserving drippings in pan; coarsely chop pancetta. Add orzo to drippings; cook over medium-high 2 to 3 minutes, stirring occasionally. Stir in chicken stock; bring to a boil. Boil 10 minutes or until liquid is absorbed. Remove from heat. Stir in olive oil and vinegar. Sprinkle with pancetta and chives.