Preheat oven to 350 degrees F. Spray baking dish with non-stick cooking spray and then pour some enchilada sauce on that.
In a large pan over medium high heat, add the oil and onions, cooking until translucent. Add the chicken, stirring just until combined. Pour 1/2 cup of enchilada sauce over that and stir. Add the sour cream and parsley, stirring until combined.
Turn off the heat and add about 2 cups of the cheese. Stir until it is fully combined.
Fill the tortillas with the chicken mixture, add some enchilada sauce over that and roll it up. Place in the baking dish, seam side down. Repeat until baking dish is full.
Pour enchilada sauce over the top of that and then the rest of the cheese. Cover with foil. (at this point you can put it in the fridge and save it to bake later.
Bake for about 20 minutes (longer if you kept it in the fridge), then remove the foil and cook for another 5 or until cheese is golden brown and bubbly and tortillas edges have crisped up a bit.
Remove from oven, add a little more chopped parsley and enjoy!