Cut paneer into cubes. To a large bowl, add 3 tablespoons cornstarch, 3 tablespoons flour along with salt, pepper.
Add 1/2 cup water to make a free flowing batter, it should neither be thick nor thin.
Heat oil in a wok/kadai on medium heat to deep fry the paneer.
Dip each paneer cube into the batter. And then add them into the hot oil.
Fry the paneer pieces til golden brown and crispy from both sides. Drain the fried paneer on paper towel.
In a bowl add soy sauce, rice vinegar, green chili sauce, tomato ketchup and sugar. Mix well combined and set aside.
In another bowl mix 1 tablespoon cornstarch with 3 tablespoons water until cornstarch dissolves completely and set aside.
Heat oil in wok on high heat. Once oil is hot, add the ginger, garlic, celery and green chili. Saute for a minute.
Then add the quartered onion and peppers. Cook for 2 minutes. Veggies should remain crunchy and you should cook on high heat.
Add in the prepared sauce and mix and lower heat to medium.
Then add in the prepared cornstarch slurry. Mix well, sauce will begin to thicken. Add additional 3 to 4 tablespoons water.
Stir in the fried paneer cubes. Toss to combine the paneer with the sauce.
Turn off heat and garnish with green onions.