In a small bowl, place all the ingredients, including the cornstarch, and whisk to combine. Set aside.
For the chicken
Trim the chicken breasts of any fat. Slice the breasts into thin slivers, each about 1/8 inch thick and 1 to 2 inches long, and set it aside.
In a medium-size mixing bowl, place two tablespoons of the taco seasoning, including the cornstarch. Add the sliced chicken breasts, and toss to combine. Add the remaining taco seasoning mixture, and toss again to combine.
Let the chicken rest at room temperature for about 30 minutes while you make the cole slaw. (See Recipe Notes)
When the chicken is ready, drizzle the cooking oil into a nonstick wok or other large skillet, and turn the heat on to medium. Add the prepared chicken pieces to the pan and separate them from one another a bit.
Cover the pan and allow the chicken to cook, undisturbed, for 2 minutes. Uncover the pan, stir the chicken around, flipping the pieces over as best you can.
Replace the cover and continue to cook for another 3 minutes. Uncover the pan, add more taco seasoning by the quarter teaspoonful if you like, and stir the chicken briefly.
Allow the chicken to finish cooking, mostly undisturbed, until it darkens in color and registers at least 165°F on an instant read thermometer.
For the cole slaw
In a medium-size mixing bowl, place the mayonnaise, vinegar, and salt, and whisk to combine well.
Add the shredded cole slaw, and toss to coat the shredded slaw completely in the dressing. Place the cole slaw in the refrigerator to chill.
For the spicy sour cream
In a small bowl, place the sour cream and Sriracha, and whisk until smooth.
For serving
When you're ready to serve the tacos, begin by warming the corn tortillas. You can warm them in a single layer in a 300°F oven or toaster oven in a single layer on a baking sheet, for about 5 minutes, or until pliable. You can also wrap the stack of them in a moistened paper towel and microwave on high for 20 or 30 seconds.
To assemble each taco, hold a warmed corn tortilla in the palm of one hand. Remove the cole slaw from the refrigerator and place about 1 tablespoon of it in a single line down the center.
Top the slaw with about 1 1/2 tablespoons of the cooked chicken, then with some chopped tomatoes, and crumbled cheese. Finish with some spicy sour cream.
Repeat with the remaining corn tortillas and fillings. Drizzle the filled tacos with some extra Sriracha and serve immediately with the lime wedges.
Video
Notes
For the chicken: If you'd like to prepare the raw chicken ahead of time, you can place it in the refrigerator for up to 1 day (provided the chicken is fresh enough to last). Before cooking it, remove it from the refrigerator and allow it to come to room temperature before cooking it.