To make the mango sauce, simply place all sauce ingredients in a food processor. Process well.
Do a taste test for salt, spice, and sweetness. Add more sugar if you find the sauce too sour. (Sourness/sweetness will depend on how ripe your mangos are). If too sweet, add a little more vinegar. If not spicy enough, add more chilli sauce. If not salty enough, add more fish sauce. If too salty, add more lime juice. Remember, the goal for this sauce is to reach a balance of sweet, sour, spicy, and salty.
Add the sauce, chicken and red pepper slices to a wok.
Stir well and bring to a boil.
Reduce to a simmer (medium-low heat), and cover. Stirring occasionally to keep from sticking, continue cooking for 30 minutes (or until chicken is well done).
Finish the dish with a sprinkling of cashews and fresh coriander.