Mix shredded chicken, 2 cups of grated cheese, 3/4 cup of tomatillo sauce, cumin, chili powder, salt and black pepper in a medium bowl and stir together.
Place flour tortillas on a large microwave-safe plate and cover with a paper towel. Microwave on high for about 30 seconds to soften the tortillas. Remove and keep covered with the paper towel until ready to assemble.
Spray a 13" x 9" baking dish with cooking spray. Place 3/4 cup of the tomatilla sauce in the bottom of the baking dish and spread it around evenly. If you are making more than 8 enchiladas you will need an additional smaller baking dish (9" x 9"). Put 6 enchiladas in the large baking dish and the remainder in the second baking dish. Divide up the 3/4 cup of enchilada sauce using 1/2 cup for the large baking dish and 1/4 cup for the smaller baking dish.
Place one flour tortilla on a large plate and add enough chicken mixture to cover bottom third of the tortilla (scant 1/2 cup). Roll the tortilla up tightly and place seam side down into the baking dish on top of the tomatillo sauce.
Fill all remaining flour tortillas with chicken filling and place in prepared baking dish.
Spoon the remaining tomatilla sauce over the tortillas and then sprinkle 1 1/2 cups of grated cheese (or more if you want it really cheesy) on top.
Bake enchiladas in the oven at 375 degrees for 25-30 minutes or until cheese is bubbly and tortillas are golden brown around the edges.
Serve enchiladas immediately and garnish with toppings as desired.
Notes: *Serve with desired garnishes such as cilantro, red or green chopped onions, sour cream or Mexican crema, avocado slices, lime slices, or my Pico de Gallo salsa. *Any cooked, shredded chicken can be used in place of rotissierie chicken. *If you want your enchiladas more saucy double the tomatillo sauce and use desired amount. *The enchiladas can be made the night before, covered and refrigerated, and baked when ready to eat. Take out of the refrigerator and bring to room temperature before baking. *Enchiladas can be frozen in a freezer safe container for up to 3 months. Unthaw completely before reheating in the microwave or oven.