Place tomatillos in a saucepan with water to cover; bring to a boil. Reduce heat to low; simmer until color begins to lighten and fruit is soft to the touch, 10 to 15 minutes.Advertisement
Transfer tomatillos to a food processor or blender. Add jalapenos, 1/3 cup cilantro, garlic, salt, and pepper; blend until smooth. Cover with plastic wrap. Refrigerate at least 2 hours for best flavor.
Preheat oven to 400 degrees F (200 degrees C).
Heat oil in a skillet over medium heat. Cook and stir chicken and onion until onions begin to brown, about 10 minutes. Add olives; cook for 5 minutes. Add cilantro; cook and stir until wilted, about 1 minute more. Remove from heat.
Line the bottom of a 8-inch square casserole dish with 2 to 3 layers of tortilla chips, breaking chips slightly. Add half of the sauce; toss with chips. Top with chicken mixture and the remaining sauce. Sprinkle cotija cheese on top.
Bake in the preheated oven until tortilla chips are softened, 15 to 25 minutes.
You can use any section of chicken meat you prefer.
Yellow onion can be substituted for the red onion.
Queso blanco or feta cheese can be substituted for the cotija cheese.
You can use the sauce immediately if you don't have time to refrigerate it.