Start heating the cooking oil for deep frying to 160 °C (320 °F). While it heats, make the glaze. Put 2 tbsp Japanese soy sauce (koikuchi shoyu), 2 tbsp mirin, 1 tbsp sake, 1 tsp sugar and 1 garlic clove (smashed flat with the side of a knife) into a cold saucepan.
Bring the glaze to a boil over medium heat, then lower the heat and simmer until it reduces to about ⅔ of the original volume. It should still pour easily, a little looser than maple syrup. Stir in 1 pinch dashi granules until they dissolve, then turn off the heat and set the pan aside.
Grind ½ tbsp ground black pepper, 1 tsp ground white pepper, ⅛ tsp garlic powder and ¼ tsp Chinese-style chicken bouillon powder together with a mortar and pestle until the pepper is ground fine. Set this blend aside with the glaze.
Pat 10 pieces chicken wings dry with kitchen paper, working into the folds and under the skin.
Put the wings in a plastic bag with 1 tbsp potato starch (katakuriko) and 1 tbsp unbleached cake flour. Trap some air in the bag and shake until the wings are evenly coated. Take each one out and shake off the excess, leaving a thin haze of white on the skin.
Check that the oil is at 160 °C (320 °F) and fry the wings in batches of 5. Lower the first batch in and fry for 4-5 minutes on each side, 8-10 minutes in total, until the wings are cooked through and only pale gold. Lift them onto a wire rack.
Rest the first batch on the rack for at least 5 minutes while you fry the next batch of 5 the same way at 160 °C (320 °F). Lift the second batch onto the rack as well.
Turn up the heat and bring the oil to 190 °C (374 °F). Once it reaches temperature, lower the first batch back in and fry for 1 minute on each side, until the wings are evenly golden brown. Lift them onto the rack and let the oil drain off.
While the first batch is still hot, brush the glaze thinly over both sides of every wing. Then dust both sides with the pepper blend, covering each wing evenly.
Fry the next batch at 190 °C (374 °F) for 1 minute on each side, lift onto the rack to drain, then glaze and dust in the same way.
Serve straight away and enjoy!
Notes
Stop the glaze while it still runs: Reduce to about 2/3, then stop. Load the brush and it should drip. Target a liquid a little looser than maple syrup. A thick, syrupy glaze drags across the skin, and the extra sugar shouts over the pepper.Brush the glaze onto a screaming hot wing: The second the oil stops dripping, brush both sides thinly. Steam pushing out of the skin holds the glaze on the surface. Wait even a minute and it soaks in, and the skin softens.Fry 5 wings at a time unless you have a giant fryer: Work in batches. Crowding the pot drags the oil temperature down hard, and oil that has dropped steams a wing instead of frying it.Cover the whole wing with the blend evenly: Both sides, evenly, and do not be shy about it. A bald patch does not fill in later, and piling more powder onto a light wing only makes it worse.Buy the smallest wings you can find: The balance between chicken and glaze is set for small wings. If your store sells only the big kind, cut the V at the joint between the flat section and the pointed tip and keep the flat.