To marinade the chicken: Place the chicken in a medium bowl with the cornflour, soy sauce, sweetener, Chinese five spice powder and salt. Using clean hands, mix thoroughly together until evenly coated. Cover and set aside to marinate for 30 minutes on the work surface.
Place the slices of ginger on a chopping board and lightly bash with a rolling pin. Break up the ginger slightly so that you have ragged looking slices. This will help release the flavour into the dish.
Spray a large frying pan or wok with low calorie cooking spray and place over medium high heat. When the frying pan or wok is really hot, add the bashed ginger slices to the pan and stir-fry for 1 - 2 minutes until turning golden and crisp around the edges.
Add the garlic slices and spring onion and stir-fry for 2 minutes until the garlic is turning golden and crisp around the edges. Take care not to burn the garlic.
Increase the heat to high and add the onion. Stir-fry for 3 - 4 minutes, until lightly golden around the edges and still crisp. Transfer the vegetables to a plate and set aside while you cook the chicken.
Return the pan to a high heat and spray with more low calorie cooking spray. When the pan is really hot, add the marinated chicken and stir fry for 4 - 5 minutes until lightly golden and sealed on all sides.
Tip the cooked vegetables from the plate into the pan with the chicken. Add the oyster sauce, soy sauce, rice wine and water and stir in. Stir fry for 3 - 4 minutes until the chicken is completely cooked through and no longer pink inside. The sauce in the pan should have thickened slightly. Take care not to overcook the chicken and vegetables, the vegetables should still retain some crispness.
Serve at once with Basmati rice and garnish with a few shreds of spring onion if wished.