Heat the oil in a large frying pan over medium-high heat. Add the onion and cook, stirring, for 2 mins or until onion softens. Add the curry paste. Cook, stirring, for 2 mins or until fragrant.
Add the coconut milk and stock. Bring to a simmer. Add the chicken, capsicum and snow peas, if desired, and cook for 2-3 mins or until chicken is cooked through.
Chop half the coriander leaves (if using) and add to the curry. Stir in the fish sauce, sugar and half the bean sprouts (if using. Squeeze over half the lime wedges. Taste and add more fish sauce, sugar and lime juice, if desired.
Top the curry with remaining bean sprouts, and coriander leaves (if using).
Serve with the rice and lime wedges.
You can use any quality green curry paste for this recipe.