In a large mixing bowl, whisk together cornstarch, salt, black pepper, garlic powder, and ginger powder until evenly combined. Add the bite-sized chicken pieces to the bowl and use your hands to thoroughly coat each piece with the mixture.

Next, crack an egg into a separate bowl and beat it until well-mixed. Pour this beaten egg over the cornstarch-coated chicken pieces, ensuring each piece gets a good coating.

In a large, deep frying pan, pour in enough oil to submerge the chicken pieces, about 2-3 inches deep. Heat the oil over medium heat until it reaches around 350°F (175°C).

Carefully add the coated chicken pieces to the hot oil in batches, ensuring not to overcrowd the pan. Fry the chicken for 5-7 minutes, turning occasionally, until they are golden brown and crispy.

In a separate pan, heat 3 tablespoons of vegetable oil over medium heat. Once hot, add the dried red chilies, minced garlic, and minced ginger. Sauté for about 1-2 minutes until fragrant.

Next, toss in the chopped onion and bell pepper. Stir fry for 2-3 minutes until the vegetables begin to soften.

In a bowl, combine soy sauce, chili sauce, vinegar, sugar, and sesame oil. Stir until the sugar is dissolved and the mixture is well combined.

Add the fried chicken pieces to the pan with the vegetables and sauce. Gently toss everything together using a spatula.

Remove the pan from heat and garnish your Crispy Chilli Chicken with freshly chopped spring onions. Serve immediately.