Add the chicken to a bowl. Open the can of enchilada sauce and pour some over the chicken. I used not quite half the can. (Keep in mind you need the rest for dipping, so don't go crazy.) Stir the chicken to coat.
Let the mixture sit for a few minutes so that the sauce has a chance to get friendly with the chicken.
Meanwhile, heat a large skillet over medium heat.
Add 1 teaspoon butter to the pan. Or don't. It's delicious to use butter, but you will still get a nice crispy quesadilla on a dry pan.
Place one tortilla on the hot pan and immediately sprinkle with cheese. Anywhere between 1/4 and 1/2 cup is fine.
Use a spoon to add some of the chicken on top of the cheese. Spread evenly. Sprinkle on some chopped cilantro if you want.
Sprinkle with more cheese, 1/4 to 1/2 cup, depending on how much of a cheese fanatic you are.
Top with another tortilla.
Continue cooking over medium heat until the bottom is light brown and crispy. Use a spatula to flip the quesadilla, and repeat on the other side.
Repeat with the remaining ingredients.
Serve with the remaining enchilada sauce for dipping. You can heat it up in the microwave if you want, or serve room temperature.