Heat groundnut oil in a large frying pan. When oil begins to smoke, quickly stir in 2 cloves minced garlic, ginger, spring onions and salt. Stir-fry until onion becomes translucent, about 2 minutes. Add chicken and stir until opaque, about 5 minutes. Add remaining 4 cloves minced garlic and stir. Add onions, cabbage, red capsicum, peas and 1/2 of the stock and cover.
In a small bowl, mix the remaining 1/2 of the stock, soy sauce, sugar and cornflour. Add sauce mixture to pan and stir until chicken and vegetables are coated with the thickened sauce. Serve immediately, over hot rice if desired.