Cut chicken into 2.5 cm (1 in) chunks.
Peel off the tough outer layers of lemongrass, leaving the tender whitish center, and chop finely.
Heat a wok or large frying pan until very hot. Add oil. Add green curry paste and stir-fry for 2 minutes. Then add chicken. Mix until coated with curry.
Add lemongrass, shallots, ginger, lime zest, fish sauce, sugar, and salt. Stir-fry for another minute.
Add peas and pour coconut milk and water. Heat to boil and then turn low to simmer for 15 minutes or until chicken is cooked through (165 Fahrenheit or 75 Celsius). Serve with plain rice.