In a large mixing bowl, combine cornflour, half of the table salt, ground black pepper, and Chinese five-spice. Toss the quartered chicken thighs in this mixture, ensuring they are evenly coated from every angle to achieve that signature crispiness. Set the coated chicken aside while you move on to heating the oil, allowing the flavors to mingle.

In a large frying pan, pour enough vegetable oil to cover the bottom to a depth of about 1/4 inch. Heat the oil over medium-high heat until it's shimmering and a tiny drop of water skitters across the surface. This should take about 3-5 minutes.

Carefully add the coated chicken thighs to the hot oil in batches, making sure not to overcrowd the pan. Shallow-fry for approximately 5-6 minutes per side or until they are golden brown and crispy. Remove them from the pan and place them on a plate lined with paper towels.

In the same pan, reserve about 1 tablespoon of the residual oil; this adds flavor to your stir-fry. Over medium heat, add the chopped onion, sliced chillies, and minced garlic. Sauté for 2-3 minutes until the onion is translucent and fragrant.

Add the fried chicken back into the pan along with the chopped spring onions. Gently toss everything together for about a minute, ensuring the chicken is heated through and coated with the flavorful mixture.

Transfer your glorious Crispy Salt and Pepper Chicken to a serving plate while it’s still hot. This dish is best enjoyed immediately.