Prepare your cooking dish by spraying with cooking spray. Place a little bit of the enchilada sauce on the bottom of the pan.
In a large skillet or non-stick pan, cook your chicken if not already cooked. (You can add your onions in while cooking the chicken and then skip step #3).
In a large skillet or non-stick pan, add a bit of olive oil and cook your onions on medium heat for a few minutes to soften them.)
To the skillet, add your sour cream, most of your cheese and the rest of your enchilada sauce. Cook until the cheese melts and the sour cream is all blended in.
Using a slotted spoon, place a little bit of the mixture into the middle of a tortilla. Roll and place in your pan. Repeat the process until all of the mixture is gone, except all of the sauce.
You should be left with more of the sauce. Pour that right on top of the enchiladas and sprinkle with the remaining cheese.
Bake at 350 for 30 minutes until heated through and cheese is nice and melty.