1.Heat oil in a large frying pan over high heat; cook onion, stirring, until softened. Add chicken; cook, stirring, until browned.
2.Add seasoning mix; cook, stirring, until fragrant. Add half the taco sauce and the water; cook over medium heat, stirring occasionally, for about 7 minutes or until mixture thickens. Remove from heat; season to taste.
3.Meanwhile, heat taco shells according to directions on packet.
4.Place chicken mixture into taco shells; top with lettuce, carrot, tomato, cheese, coriander, sour cream and remaining taco sauce.