Toss cabbage, carrot, kale, scallions and salt together in a large bowl.
Toss mixture with flour so it coats all of the vegetables.
Stir in the eggs.
Heat a large heavy skillet on medium-high heat. Coat the bottom with oil and heat that too.
To make a large pancake, add ¼ of the vegetable mixture to the skillet, pressing it out into a ½- to ¾-inch pancake. Gently press the pancake down flat. Cook until the edges begin to brown, about 3 minutes. 30 seconds to 1 minute later, flip the pancake with a large spatula. Cook on the other side until the edges brown, and then again up to a minute more.
To make small pancakes, you can grab little piles, letting a little batter drip back into the bowl, and depositing them in piles on the skillet, to form 3 to 4 pancakes. Press down gently with a spatula so they flatten slightly. Cook for 3 minutes, or until the edges brown. Flip the pancakes and cook them again until brown underneath.
Make okonomiyaki sauce by combining all sauce ingredients in a small saucepan and let simmer for 3 to 5 minutes, until smooth and thick.
Serve pancakes with sauce and any of the other fixings listed above, from Japanese mayo to scallions and toasted sesame seeds.
Extra pancakes will keep in the fridge for a couple of days or can be frozen and reheated in a hot oven until crisp again.
