Cut the paneer into equal-sized cubes. If using frozen paneer, soak it in warm water for 10 minutes to soften, then drain and pat thoroughly dry with a paper towel. Wet paneer will cause the batter to slip off during frying.

In a medium mixing bowl, whisk together 3 tbsp cornstarch, 2 tbsp all-purpose flour, 1/2 tsp ground black pepper, and 1/2 tsp salt. Gradually add about 4 tbsp water, whisking to form a smooth, thick batter that resembles the consistency of heavy cream. Toss the dried paneer cubes gently in the batter until they are fully and evenly coated.

Heat 3 tbsp oil in a wide frying pan or wok over medium-high heat. Once the oil is hot, add the battered paneer cubes in a single layer, leaving space between them. Fry for 3 to 4 minutes, turning occasionally, until a light golden, crispy crust forms on all sides. Use a slotted spoon to transfer the paneer to a plate lined with paper towels.

In a small bowl, combine 1.5 tbsp soy sauce, 1 tbsp green chili sauce, 1 tbsp red chili sauce, 1 tsp white vinegar, 1 tbsp tomato ketchup, and 1/4 tsp sugar. Stir well and set aside near the stove.

Wipe the wok clean or heat 1 tbsp of fresh oil over high heat. Add the minced garlic, minced ginger, and slit green chilies. Sauté rapidly for 30 seconds until fragrant, taking care not to let the garlic brown. Add the onion petals and green bell pepper squares. Stir-fry on high heat for 1 to 2 minutes, constantly tossing, until the edges are slightly blistered but the vegetables remain firm and crunchy.

Reduce the heat to medium. Pour the prepared sauce mixture over the vegetables and stir to combine. In a small cup, mix 1 tsp cornstarch with 3 tbsp cold water to make a smooth slurry. Pour this slurry into the pan, stirring constantly. Cook for 1 minute until the sauce bubbles, turns translucent, and thickens to a glossy glaze.

Add the fried paneer cubes back to the wok. Toss quickly for 30 seconds to coat the paneer evenly with the glossy sauce without making the crust soggy. Turn off the heat, stir in the spring onion greens, and serve immediately while hot.