01 - In a large mixing bowl, combine the chicken pieces with cornstarch, all-purpose flour, egg, salt, black pepper, soy sauce, and ginger-garlic paste. Toss until every piece is evenly coated. Let the chicken marinate at room temperature for 15 minutes.
02 - Pour vegetable oil into a wok or deep heavy-bottomed pan to a depth of about 2 inches and heat over medium-high heat to 350°F. Working in batches to avoid crowding, carefully lower the marinated chicken pieces into the hot oil. Fry each batch for 4 to 5 minutes, turning occasionally, until the exterior is deep golden brown and crisp. Transfer the fried chicken to a plate lined with paper towels to drain.
03 - In a clean large wok, heat 2 tablespoons of vegetable oil over high heat until it just begins to shimmer. Add the minced ginger, garlic, and slit green chilies. Stir-fry vigorously for 30 to 45 seconds until fragrant and the aromatics are lightly golden.
04 - Add the diced onion and both bell peppers to the wok. Toss continuously over high heat for 2 to 3 minutes, keeping the vegetables in constant motion. They should soften slightly at the edges while retaining a crisp, vibrant bite.
05 - Add the fried chicken pieces back into the wok and toss everything together so the chicken is well distributed among the vegetables.
06 - Pour in the soy sauce, chili sauce, tomato ketchup, vinegar, sugar, black pepper, and a pinch of salt. Stir thoroughly to coat every piece of chicken and vegetable in the sauce mixture.
07 - Give the cornstarch slurry a quick stir and pour it into the wok. Continue tossing over high heat for 1 to 2 minutes until the sauce thickens into a glossy coating that clings tightly to the chicken and vegetables.
08 - Remove the wok from the heat and scatter the sliced green onions over the top. Serve immediately as a standalone appetizer or alongside steamed jasmine rice or vegetable fried rice as a main course.