Mix 1 cup of all-purpose flour, ¼ teaspoon of kosher salt, ¼ teaspoon of sugar, and ¼ teaspoon of baking powder. Stir in 160g of peeled, grated nagaimo and ¾ cup of dashi. Cover and refrigerate for 1 hour.
Finely chop 640g of green cabbage and drain well. Chop ¼ cup of pickled red ginger. Cut 225g of thinly sliced pork belly into 4in / 10cm strips.
Mix 4 large eggs, ½ cup of tenkasu and two-thirds of the ginger into the batter. Fold in the cabbage in stages until well coated.
Heat a lightly oiled skillet over medium heat. Spread batter into 6in / 15cm rounds, about ¾in / 2cm thick. Distribute the pork over the tops.
Cover and cook over medium-low heat for 5 minutes. Flip, cover and cook for another 5 minutes. Flip again and cook uncovered for 2 minutes, until cooked through. Repeat with the remaining batter.
Brush with okonomiyaki sauce, drizzle with Japanese mayonnaise and add the reserved ginger.
