To make the sauce, drain both the pineapple tins in a sieve over a bowl and keep all the juice –
you should have about 250ml. Add 300ml water, then stir in the soy sauce, vinegar, sweetener, ketchup and chilli flakes until
thoroughly combined. Set aside. Put the cornflour in a bowl and stir in approx three
tablespoons (or more) if required of water to make a smooth paste.

Cut each chicken breast into eight or nine even pieces. Heat the oil in a
large non-stick frying pan or wok and stir-fry the onion and peppers for two minutes over
a high heat. Drain the water chestnuts and cut them in half horizontally.

Add chicken to the pan and stir-fry for two minutes until coloured
on all sides. Add the garlic, ginger, pineapple chunks and water chestnuts and stir-fry for
30–60 seconds.

Give the cornflour and water mixture a good stir and add it to the pan with the chicken and
vegetables. Stir well, season with some ground black pepper and bring to a simmer.
Cook for 4–6 minutes until the sauce is thickened and glossy and the chicken is tender and
cooked throughout, turning the chicken and vegetables a few times. Serve with a small portion of rice.