½cupmirin,storebought or homemade (see link below)
¼cupsake
¼cupJapanese soy sauce or regular soy sauce (such as kikkoman)
2tablespoonssugar
4large boneless skinless chicken thighs
Kosher salt
Black pepper
Canola oil
1green onion,green part only, cut into rings and/or ground sansho pepper
Instructions
Combine the mirin and sake in a small saucepan. Heat over medium-low for 5 minutes, then add the soy sauce and sugar. Stir until dissolved. Adjust the heat to simmer for 20 to 25 minutes, until reduced by about a third and thickened. There should be a very generous ½ cup. Set aside to cool and concentrate. Use or store in a jar in the fridge for a week. Return to room temperature before using.
Rinse and pat the thighs dry with paper towel. Poke it with a toothpick or fork to let flavors penetrate. Sprinkle with salt and pepper. Heat a medium skillet over medium heat. Add a small splash of oil. Cook the thighs, smooth side down, for 3 minutes, or until a little golden underneath. Turn each piece over, lower the heat to medium-low or low, then cover; you want a gently hiss. Cook for 8 minutes, or until just cooked through.
Add about 2 tablespoons of the sauce. Turn to coat the chicken, increase the heat to medium. Let the chicken cook in the bubbling sauce for 3 to 5 minutes, turning often, until the sauce has coated the chicken with a reddish-brown gloss. The pan will be have some fat from the chicken as well as the cooked down dark-colored teriyaki sauce.
Transfer the chicken to a plate and let cool for 5 to 10 minutes. Cut across the grain, arrange on a plate and garnish with a sprinkling of green onion and/or sansho pepper. Serve with rice.