Place the chicken pieces, cornflour and sesame oil in a bowl and stir together. Add the chicken to the wok and stir-fry until it has taken a little colour. Remove the chicken from the pan and place in a strainer, saving the oil.
Pour some of the strained oil back into the wok and reheat. Add the shallots, ginger and garlic and cook for 3 minutes. Add the curry paste, tamarind paste, fish sauce, tamari soy sauce, chicken stock, sugar and coconut milk and cook for 3 minutes. Add the chicken and lime juice and simmer for a further 5 minutes.
Finally stir in the basil and coriander and check the seasoning. Serve with steamed rice.