Photo: Schellack (CC BY 3.0) via Wikimedia Commons · source
Binchotan burns hot without flames, so the chicken browns fast while the inside stays juicy. A charcoal grill with a narrow bed of coals, or the broiler, does the job; the glossy tare is what makes it taste like a Tokyo counter.
1 chicken wing or a few roasted chicken bones (optional, for depth)
For negima: 600 g (1 1/3 lb) boneless skin-on chicken thighs, cut into 3 cm (1 1/4 in) pieces
6 scallions (white and light green), cut into 3 cm lengths
For tsukune: 400 g (14 oz) ground chicken thigh
1 tbsp grated ginger
2 scallions, minced
1 tbsp potato starch or cornstarch
1/2 tsp salt
To finish: 1 tsp coarse salt, shichimi togarashi, 4 egg yolks for dipping (optional)
16 bamboo skewers, soaked 30 minutes
How to make it
Make the tare (25 min): Simmer the soy, mirin, sake, sugar and the wing in a small pan over low heat until reduced by about a third and syrupy, about 20 minutes. Strain into a narrow cup for dipping.
Skewer (20 min): Thread the thigh pieces on skewers alternating with scallion, 4 pieces of chicken per skewer, pushed close together. For tsukune, knead the ground chicken with the ginger, scallions, starch and salt for 2 minutes until sticky, shape into 8 oval logs about 8 cm long around the skewers with wet hands, and chill 10 minutes.
Heat (20 min): Build a narrow, hot bed of charcoal and set two bricks or rails on either side so the skewers rest above the coals without touching the grate. Or heat the broiler with the rack 8 cm (3 in) from the element, skewers on a foil-lined pan with the ends shielded by foil.
Grill (10 to 12 min): Grill the negima turning every minute or so until browned and just cooked through, 8 to 10 minutes; season half with coarse salt and dip the other half in tare twice in the last 2 minutes. Grill the tsukune 8 to 10 minutes, turning, then dip in tare and grill 30 seconds more to glaze, twice.
Serve (2 min): Serve straight off the grill, salt skewers first, then tare. Shichimi on the side, and the tsukune with a raw egg yolk for dipping.
Tips
Fan the coals for a burst of heat to crisp the skin.
Keep the tare in the fridge; it gets better each time you dip.
Cut every piece the same size or they cook unevenly.