Make the tare sauce

• Add the mirin, sake, soy sauce, and brown sugar to a saucepan. Place the pan over medium heat and bring the mixture to a gentle boil, stirring with a wooden spoon to dissolve the sugar. This should take about 4–5 minutes. Keep the pan uncovered and watch closely so it does not boil over.
• Once the sauce comes to a boil, reduce the heat to medium-low. Simmer for about 10 minutes, stirring occasionally, until the sauce thickens slightly.
• Remove the pan from the heat and let the sauce cool. Transfer it to a jar for storage. The sauce will thicken more as it cools. The final texture should be glossy and lightly syrupy, but still pourable. It should not be overly thick or gloopy.

Prepare and marinate the chicken

• Slice the chicken thighs into long strips, about 1 inch wide. Transfer them to a storage container.
• Once the tare sauce has cooled to room temperature, add 6 to 8 tablespoons of the sauce to the chicken. Gently massage to coat. Cover and marinate in the refrigerator for at least 2 hours or overnight.
• Keep the remaining tare sauce separate and clean for brushing and serving. Do not reuse the sauce that touched the raw chicken. Discard the marinade after using.

Thread the skewers

• Trim away the scallion roots. Slice each scallion to separate the white and green parts. For this recipe, use only the white and pale green parts, where the texture is firmer and not hollow in the center. Cut each scallion white into 3 equal sections.
• To thread the skewers, add one piece of scallion white, followed by one piece of chicken. Fold the chicken into a loose C shape 2 to 3 times as you thread it onto the skewer. Alternate chicken and scallion until you reach near the top of the skewer, leaving about a 1 to 1½-inch gap at the top.
• For reference, each skewer should have about 4–5 pieces of chicken. Place the skewers on a large lined sheet pan.
• Lightly sprinkle each skewer with salt and pepper, then spray with avocado oil.

Cook the skewers

Air fryer method:

• Line the air fryer basket and air fry at 380°F for 6 minutes. Rotate the skewers, brush with more clean tare sauce, and air fry for another 5 minutes, or until the chicken is cooked through. Brush with more tare sauce once the skewers come out of the air fryer.

Oven broiler method:

• Preheat the broiler for 5 minutes. Place the skewers on a lined sheet pan. Broil for 7 minutes on the first side. Flip the skewers, brush with clean tare sauce, and broil for another 6 minutes, or until the chicken is cooked through. Brush with more tare sauce once the skewers come out of the broiler.

Stovetop grill pan method:

• Preheat a grill pan over medium heat until the pan is hot but not smoking. Lightly oil the ridges of the pan.
• Place the skewers on the pan and gently press them down so the chicken and scallions make good contact with the ridges. Let them cook undisturbed for 5 to 6 minutes, so they develop grill marks and release more easily.
• Flip the skewers and cook for another 5 to 6 minutes. At this point, the chicken should be almost cooked through.
• Lower the heat to low. Brush the top side of the skewers with clean tare sauce, then flip them sauce-side down against the pan for about 30 seconds to caramelize. While that side caramelizes, brush the new top side with sauce. Flip one more time and cook for another 30 seconds to caramelize the second side.

How to serve it:

• Remove the skewers from the pan right away. Brush with more tare sauce before serving. The skewers will be hot, so handle them carefully. Serve hot or warm.