Slice the chicken into strips that are 1/4 inch thick.
Peel mango and slice into 1/4 inch strips. Reserve.
Heat oil in wok on high heat, until it is just about to smoke. Add garlic and onions and stir-fry 30 seconds. Add reserved chicken and water and stir-fry about 2 minutes until chicken is springy. Add soya and sugar and stir-fry for 1 minute. Add chili paste and lime juice, stir-fry for 1 minute. Add cashews and stir-fry for a final minute.
Transfer to a serving dish and serve with steamed rice.