For the chicken balls, place the chicken, spring onions, Chinese five-spice powder, crushed garlic, red chilli and soy sauce into a bowl and mix to completely combine.
Mould the mince mixture into golf ball-sized balls, then dredge in cornflour.
Heat the vegetable oil in a deep-sided non-stick frying pan over a medium heat. Add the chicken balls and fry for 8-10 minutes, turning regularly, until golden-brown all over and completely cooked through. Remove from the pan and drain on kitchen paper.
For the sauce, place the cornflour, water, sugar, soy sauce, vinegar and ketchup into a pan over a medium heat and mix well. Cook, stirring constantly, for 5-6 minutes, then add the peppers, pineapple chunks and spring onion and stir well.
To serve, place a large spoonful of cooked white rice onto each plate and place 3-4 chicken balls on top. Pour the sauce over and serve.