Add the cornflour, salt, black pepper, garlic powder, and onion powder in a mixing bowl.
Gently coat the chicken pieces with the cornflour mixture until they are evenly covered.
Heat vegetable oil in a deep pan or wok over medium-high heat.
Carefully add the coated chicken pieces to the hot oil and fry until they turn a golden brown and become crispy, which should take approximately 5-7 minutes. Remove the chicken from the oil and place them on a paper towel to drain.
In a separate pan, heat 2 tablespoons of vegetable oil over medium heat.
Add minced garlic and ginger to the pan and stir-fry for about 30 seconds until they release their fragrant aroma.
Mix the chilli sauce, tomato ketchup, soy sauce, rice vinegar, and brown sugar in the pan. Allow the sauce to simmer for a few minutes until it thickens slightly.
Add the cornflour-water mixture into the sauce to further thicken it. Stir thoroughly until the sauce reaches your desired consistency.
Add the crispy chicken pieces to the sauce and toss them to ensure an even coating.
Serve your Crispy Chilli Chicken while it’s hot, optionally garnished with chopped spring onions or sesame seeds according to your preference.