Toss the chicken pieces in the cornflour and season well. Set them aside.
Fry the onion in half of the oil in a wok on a low to medium heat, until it softens – about 5-6 minutes – then add the garlic and cook for a minute. Stir in the spices and sugar and cook for another minute, then add the stock and soy sauce, bring to a simmer and cook for 20 minutes. Tip everything into a blender and blitz until smooth.
Wipe out the pan and fry the chicken in the remaining oil until it is browned all over. Tip the sauce back into the pan and bring everything to a simmer, stir in the peas and cook for 5 minutes. Add a little water if you need to thin the sauce. Serve with rice.