Begin by washing and patting dry the chicken. Cut the chicken into small, bite-sized cubes, then coat with cornstarch, all-purpose flour, ginger garlic paste, salt, and black pepper. Let marinade sit for about 10 minutes.

Heat neutral oil in a large frying pan or wok over high heat until shimmering. Add half of the coated chicken, frying until golden brown and crispy, about 6-7 minutes. Drain on paper towels and repeat with remaining chicken.

In the same wok, add cooking oil over medium heat. Once hot, add minced garlic and sliced green chilies, sautéing briefly. Then, add sliced onion and bell pepper, cooking for 2 minutes until vegetables soften.

Prepare a slurry by mixing cornstarch with water in a bowl. Pour this into the wok, then add dark soy sauce, sweet chili sauce, red chili paste, tomato ketchup, and rice vinegar. Stir and cook for about 3-4 minutes to thicken.

Add the fried chicken and diced mango to the wok, mixing gently for about 2 minutes until heated through. Garnish with chopped spring onion greens and serve immediately with rice or noodles.