Step 1

Position oven rack about 8 inches from heat source; heat broiler. Season chicken thighs with salt and pepper; set thighs skin side up on broiler pan (or foil-lined rimmed baking sheet fitted with flat wire rack), tucking exposed meat under skin and lightly flattening thighs to be of relatively even thickness (see illustration 6). Broil until skin is crisp and golden brown and thickest parts of thighs register 175 degrees on instant-read thermometer, 8 to 14 minutes, rotating pan halfway through cooking time for even browning.

Step 2

While chicken cooks, combine soy sauce, sugar, ginger, and garlic in small saucepan; stir together mirin and cornstarch in small bowl until no lumps remain, then stir mirin mixture into saucepan. Bring sauce to boil over medium-high heat, stirring occasionally; reduce heat to medium-low and simmer, stirring occasionally, until sauce is reduced to 3/4 cup and forms syrupy glaze, about 4 minutes. Cover to keep warm.

Step 3

Transfer chicken to cutting board; let rest 2 to 3 minutes. Cut meat crosswise into 1/2-inch- wide strips. Transfer chicken to serving platter; stir teriyaki sauce to recombine, then drizzle to taste over chicken. Serve immediately, passing remaining sauce separately.