Put the chicken in a bowl with the egg white, sesame oil, cornflour and 1 tsp salt, and mix well. Chill for 20 mins.
If you are using oil for velveting the chicken, heat a wok until very hot and then add the oil. When it is very hot, remove the wok from the heat and immediately add the chicken, stirring vigorously to prevent it sticking. After about 2 mins, when the chicken turns white, quickly drain it and all of the oil into a stainless steel colander set over a bowl. Discard the oil. If you are using water instead of oil, do exactly the same but bring the water to the boil in a saucepan before adding the chicken. It will take about 4 mins for the chicken to turn white in the water.
If you have used a wok, wipe it clean. Heat it until it is very hot, then add the 2 tsp of groundnut oil. Add the cashew nuts and stir-fry for 1 min. Add the rice wine or dry Sherry and soy sauce. Return the chicken to the wok and stir-fry for 2 mins. Scatter over the spring onions and serve immediately.