To make the sauce, mix all the ingredients and keep it aside.
In a wok heat 2 tablespoons of Oil. Add cashews and cook for 3-4 minutes. Keep stirring continuously for even browning (Keep a close eye towards the end, else the cashews will burn in no time and will taste bitter).
Using a slotted spoon, remove cashew from the wok draining excess oil. Keep the cashews aside.
Cut chicken breast to bite-size pieces. Sprinkle cornstarch and pepper. Toss to coat chicken well.
Add coated chicken breast to the same hot wok (there would be remaining oil after frying cashews).
Separate any chicken pieces stuck together and cook on high heat for 2 minutes. Flip and cook for another minute. Using a slotted spoon remove the chicken pieces. Then chicken needs to be just cooked through. (It will get cooked further along with the sacue later)
Add the remaining 1 tablespoon oil. Add dry red chilli, chopped garlic, birds eye chilli (if using) , white parts of the green onion. Saute on high heat for 30 seconds, until the garlic is aromatic.
Add red pepper. Saute for another 30 seconds.
Add cooked chicken, roasted cashew and stir fry sauce. Toss everything well and cook for about 1 minute until the sacue has thickened and coats the chicken well.
Switch off the flame and stir in the green onion.
Serve with rice/noodles or as an appetizer.