Cut each chicken breast into approximately three pieces.
Place the chicken in a pot and pour the enchilada sauce over it. Cook covered on low to medium heat for about 20 minutes, stirring occasionally.
Once the chicken is cooked through, remove it from the pot, and shred it into bite-sized pieces using two forks.
Baking
Preheat your oven to 375°F.
In a baking dish, start layering: ¼ cup of enchilada sauce at the bottom, two tortillas, ⅓ of the shredded chicken, ⅓ of the remaining enchilada sauce, and ⅓ of the cheese. Repeat these layers three times.
Bake the casserole uncovered for 20 to 30 minutes until the cheese melts and starts to brown.
Garnish with chopped green onions or cilantro if desired. Serve warm.
Notes
Leftovers reheat well in an airtight container in the microwave.
Consider adding diced jalapeños for heat or using different cheese varieties.