Slice the fish diagonally into pieces (sogi-giri). Sprinkle with the (A) seasonings and let sit for about 10 minutes. Pat dry to remove excess moisture. Separate the leaves from the mitsuba stems and cut the stems into 2-cm long pieces. Halve the sudachi crosswise.
For the sauce, heat the dashi stock in a sauce pan and add the (B) seasonings. Add the (C) mixture to thicken the sauce. Add the white leek and remove from the heat.
Flour the (1) fish and deep fry in the oil at 170oC until golden brown and crispy. Place the fish on a dish and cover with the (2) sauce. Top with the mitsuba and ito-togarashi and garnish with the sudachi.