Dice chicken into 3/4-inch pieces. Set aside.
Heat oil in a heavy skillet on medium-high heat. Add onions and fry until golden brown. Stir in ginger and garlic. Add chicken pieces and fry until chicken starts to turn white, about 5 to 7 minutes.
Stir in the simmer sauce and bring to boil. Reduce heat, cover and simmer for about 10 minutes; stir occasionally.
Transfer to a serving dish. Garnish with the cashews. Serve with rice or flat bread.