In a large bowl put all-purpose flour, corn starch, salt, and pepper. Mix everything. Add water and around ½ a tablespoon of oil, mix to make a lump free batter.
Add cauliflower florets to the batter and mix everything until the batter evenly coats the florets.
Take florets one by one, gently tap to remove excess batter, and place on a baking tray covered with a baking sheet. Bake in a pre-heated oven at 200°C (around 400°F) for around 25-30 minutes or until the cauliflower florets start turning brown.
While the cauliflower florets are getting baked, heat oil in a wok. Add onion, ginger, garlic, chili pepper, and white part of spring onion. Saute until the onion turns translucent.
Add spring onion greens and saute for about a minute.
Add soy sauce, chili sauce, tomato paste, and vinegar. Mix everything and cook for about a minute.
Finally, add baked cauliflower florets and mix until the sauce evenly coats all the florets. Cook for about a minute.
Garnish with chopped spring onion. Enjoy as an appetizer or in the main course with some rice or noodles.