or the batter: Whisk flour, corn starch, baking powder, salt, eggs, water and ice cubes in a bowl until incorporated. Let sit on the counter for 10 minutes until ice cubes are melted. The batter will be thick. This is good.
Gochujang sauce: combine all sauce ingredients (sugar, water, garlic, sesame oil, mirin and gojuchang sauce) in a blender or a food processor and blend until smooth. Set aside.
or the cauliflowers: Spinkles salt, pepper, garlic powder and corn starch over the cauliflower.
Add the cauliflowers to the flour batter, stirring to coat.
In a heavy bottom skillet, heat oil over medium high heat. The oil should be high enough to cover the cauliflowers, about 2 inches. Working in batches, lift the cauliflower florets from the batter, shaking off excess flour. Drop the cauliflowers to the skillet and fry for a few minutes on each side, turning occasionally until the coating is golden brown and crunchy. Remove and set on a plated line with paper towel.
Let the cauliflowers cool down completely, at least 10 minutes before adding to the sauce. This will ensure the florets will be crunchy and not soggy.
Add the cauliflowers to the sauce, toss to coat. Use a slotted spoon to transfer to a serving plate. Garnish with toasted sesame seeds and green onion. Serve