Heat the oil in a medium pan, add
the onion and fry for 2 mins. Tip
in the paste and cook for 1 min more.
Pour in the coconut milk, fish sauce,
lime zest and juice, and peppercorns.
Bring to a simmer, then add the beans
and chicken. Cook for 5 mins or until
the chicken is cooked through.
Just before serving, add the basil
leaves. Serve with basmati rice.