Prepare the Chicken Coating: In a shallow bowl, mix the cornflour, plain flour, salt, and white pepper. In another bowl, have your lightly beaten egg ready. This two-stage coating station makes the process much tidier.

Coat the Chicken: Dip each piece of chicken first into the beaten egg, letting any excess drip off, then dredge it thoroughly in the flour mixture. Make sure every piece is well-coated. Set the coated chicken pieces on a plate or wire rack for 5 minutes. This little rest helps the coating adhere properly during frying.

Fry the Chicken: Pour enough vegetable oil into a large wok or deep frying pan to come about 2.5cm (1 inch) up the sides. Heat over a medium-high heat to around 175°C. To test if it’s ready without a thermometer, drop a small piece of batter in; it should sizzle immediately and turn golden in about 30 seconds. Carefully add half the chicken pieces to the hot oil. Frying in batches is crucial to avoid overcrowding the pan, which would lower the oil temperature and result in soggy chicken. Fry for 4-5 minutes, turning occasionally, until golden brown and cooked through. Remove with a slotted spoon and drain on a wire rack. Repeat with the remaining chicken.

Start the Sauce: Carefully pour out most of the oil from the wok, leaving about 1 tablespoon behind. Return the wok to a medium heat and add the onion and peppers. Stir-fry for 3-4 minutes until they just begin to soften but still have a bit of a crunch.

Simmer the Sauce: In a jug, whisk together the reserved pineapple juice, soy sauce, rice vinegar, brown sugar, and tomato ketchup. Pour this mixture into the wok with the vegetables. Bring it to a gentle simmer.

Thicken the Sauce: Once simmering, give your cornflour slurry a quick re-stir and pour it into the sauce, stirring continuously. Let it bubble for 1-2 minutes until the sauce thickens to a glossy consistency that can coat the back of a spoon. What works best for me is to watch it closely; it thickens quite suddenly!

Combine and Serve: Add the pineapple chunks and the crispy fried chicken to the wok. Gently toss everything together for about 30 seconds until every piece of chicken is coated in the glorious sweet and sour sauce. Serve immediately, garnished with sliced spring onions and a sprinkle of sesame seeds, alongside fluffy rice.