In a large bowl, combine cornflour, half the table salt, half the ground black pepper, and the Chinese five-spice. Add quartered chicken thighs to the mixture, ensuring they’re completely coated. Allow the chicken to sit for about 10 minutes.

In a wok or large frying pan, pour in enough vegetable oil to cover the bottom about 1 inch deep. Heat the oil over medium-high heat until it shimmers, about 5 minutes.

Carefully add the coated chicken thighs to the hot oil in batches, frying for 5-7 minutes until golden brown and crispy. Remove and drain excess oil on paper towels.

In the same wok, remove excess oil, leaving about 1 tablespoon. Add chopped onions, minced garlic, and sliced chillies, stirring for 2-3 minutes.

Return the crispy chicken to the wok, tossing it gently with the stir-fried onion mixture. Sprinkle in the remaining salt and black pepper, and stir-fry for an additional 1-2 minutes before serving.