In a 10-inch nonstick skillet, heat the vegetable oil over medium-high heat. Add the boneless skinless chicken breasts and cook 7 to 9 minutes, stirring occasionally, until no longer pink in centre. Sprinkle in the package Old El Paso™ Chicken Taco Seasoning Mix and pour in the water. Stir well, then heat to boiling. Reduce heat; simmer uncovered 3 to 4 minutes, stirring frequently, until thickened and the chicken is cooked through and coated.

While the chicken mixture is cooking and thickening, heat the Stand ‘N Stuff™ shells as directed on the package. Prepare the make it fresh toppings by getting the shredded cheddar cheese, shredded lettuce, diced avocado and diced tomato ready in small bowls. Divide the hot chicken mixture among the warm shells, then add shredded cheddar cheese, shredded lettuce, diced avocado, diced tomato and any remaining make it fresh toppings on each taco before serving.