Quick and easy chicken with Asian flavors. My husband saw it in Cook's Country and asked me to try it--we all loved it! To use as a make-ahead meal, portion out the chicken and place in a zip-loc bag. Measure sauce ingredients in a second bag.
Dry chicken thoroughly with paper towels and season with pepper. Heat oil in large nontstick skillet over medium-high heat until shimmering. Cook chicken, skin side down (thighs will fit into pan snugly), until skin is deep brown and crisp, (15 to 20 minutes). Chicken should be moderately brown after 10 minutes. If too browned, reduce heat; if pale, increse heat. Turn chicken over, reduce heat to medium, and cook until second side is brown and meat is thoroughly cooked, about 10 minutes.
Meanwhile, whisk soy sauce, sugar, mirin, ginger, garlic, and cornstarch together in small bow.
Transfer chicken to plate and pour off fat. Add soy mixture to skillet and return to medium heat. Return chicken to skillet, turn to coat with sauce, and simmer, skin side up, until sauce is thick and glossy, about 2 minutes.
Transfer chicken to serving platter and sprinkle with scallions. Pour remaining sauce into small bowl and pass separately.