In a bowl, mix cornflour, maida, salt, pepper, and water into a thick batter. Toss in the paneer cubes until evenly coated.
Shallow-fry (or deep-fry) paneer pieces in hot oil on medium heat until golden and crisp. Remove and drain on paper towel.
Heat 1–2 tbsp oil in a wok. Add garlic, ginger, and green chilies. Sauté on high heat for 30–40 seconds until aromatic.
Add cubed onion and capsicum. Stir-fry on high heat for 1–2 minutes. Keep them slightly crunchy for restaurant-style texture.
Add soy sauce, chili sauce, ketchup, and vinegar. Stir quickly on high heat. Adjust salt if needed (soy is already salty).
For semi-dry version, add a slurry of 1 tsp cornflour in 2 tbsp water. Stir till it thickens and coats the back of a spoon.
Add fried paneer cubes. Toss well to coat with sauce. Garnish with chopped spring onions.