Potential garnishes: Kewpie mayonnaise, okonomiyaki sauce, sesame seeds, green onions, chopped nori, bonito flakes, Sriracha sauce.
Stir together dry ingredients (flour, cornstarch, baking powder, sugar, and salt). In a separate bowl, combine dashi, soy sauce, sesame oil, and eggs.
Combine all, being careful to stir as little as possible (to not increase gluten). Refrigerate for one hour.
Add cauliflower, cabbage, and green onions to chilled mixture.
Heat skillet with half of the oil. When hot, add 1/4 of the batter to the pan, using spatula to form a pancake shape. Reduce heat to medium and cook for five minutes or until first side is browned (do not burn). Flip and cook four to five more minutes. Repeat four more times.
Garnish okonomiyaki with toppings and serve.