Remove the core and tough parts of the stems from the 400 grams cabbage and shred it.
400 grams cabbage
In a large bowl, combine the shredded cabbage, 60 grams scallions, 10 grams katsuobushi, and 140 grams all-purpose flour, tossing with two large forks or your fingers to distribute everything evenly.
60 grams scallions, 10 grams katsuobushi, 140 grams all-purpose flour
Peel the 280 grams nagaimo and grate it into a separate bowl. You can also roughly chop it and puree it in a food processor.
280 grams nagaimo
Add the 2 large eggs and ½ cup dashi stock, and whisk together until the everything is uniformly incorporated.
2 large eggs, ½ cup dashi stock
If you want to add other filling ingredients, this is the time to do it. Decide whether your additions will incorporate better into the dry ingredients or wet ingredients and mix them in accordingly.
Pour the wet ingredients into the cabbage mixture and stir together until all the cabbage has been moistened and there are no large lumps of flour, but be careful not to overmix. It's fine if there are still some small clumps of flour.
Lay out the 9 slices bacon in a cold pan, overlapping slightly to account for shrinkage. If you aren't using bacon, you'll need to add a few teaspoons of vegetable oil to the pan.
9 slices bacon
Add a third of the cabbage mixture into a mound on top of the bacon. Press down on the mound using a spatula to flatten out the top and then push the edges back towards the center to make a round pancake that's roughly the same thickness from edge to edge (it should be about ¾-inch thick).
Cover with a lid and cook until the bottom is well browned (about 7 minutes).
Flip the okonomiyaki. If you are unsure about your flipping abilities, lightly oil and preheat a second pan, then you can use the second pan to cover the first and flip the okonomiyaki straight into the second pan using oven mitts to hold the hot pans.
Press down on the top of the okonomiyaki with a spatula and cook uncovered until the second side is browned as well (about 7 minutes).
Slide the okonomiyaki out of the pan onto a plate and top with okonomiyaki sauce, mayonnaise, aonori, katsuobushi and benishoga.
okonomiyaki sauce, mayonnaise, aonori, katsuobushi, benishoga