Shred the cooked chicken or finely chop it on a cutting board. I often use a rotisserie chicken or my poached chicken for this.
Make the filling:
In a large cast iron skillet, combine the shredded chicken and enchilada sauce and toss to coat. Bring the mixture to a boil over medium-high heat, reduce the heat to low, and simmer for 3 to 5 minutes, stirring, to heat the chicken through. Remove the pan from heat.
In a medium bowl, combine the cheese. Add 1 ½ cups (180 g) of the cheese to the chicken mixture in the skillet and toss to combine. Cover and set aside for 2 minutes to melt the cheese through while you prepare the remaining ingredients.
Assemble:
Assemble each taco by placing a scoop of the enchilada mixture onto a tortilla and topping with cheese, sour cream, guacamole, sliced olives, and cilantro.