In a large skillet, saute onion and red capsicum in oil for 2-4 minutes or until crisp-tender. Add the chicken, curry, ginger, garlic, salt and cayenne. Cook and stir for 5 minutes. Stir in the mango, coconut milk and tomato paste; bring to a boil. Reduce heat; cover and simmer for 10 minutes or until chicken is no longer pink. Serve with rice if desired.