Add all ingredients (A) in a large mixing bowl and mix with a whisk.
Pour the Dashi broth and the grated potato, and the sake in the bowl.
Let the batter rest in a fridge at least for 3 hours.
Chop the cabbage into small pieces.
Grease a frying pan and heat it.
Prepare another small bowl and add three handfuls of the chopped cabbage, 2 tbsp of Okonomiyaki batter, and 1 egg. Mix them about 3 times. Don't mix them too much.
Spread the Okonomiyaki batter mixed with the cabbage on the heated frying pan as soon as you can. Add the toppings and cover the frying pan with a lid. Braise it for a while.
When the Okonomiyaki becomes golden brown, flip it over and braise until the Okonomiyaki is cooked.
Serve on a plate and dress Okonomiyaki sauce and mayo. Sprinkle some bonito flakes and Aonori.
