Preheat oven to 350° F.
Spray an 8x8 inch baking dish with non-stick cooking spray. Rip two tortillas into large pieces and layer the bottom of the dish, trying to cover as much as possible. Spread 1/3 of sauce over the tortilla pieces. Cover sauce with 1/2 of the chicken, 1/2 of the onions and top them with 1/3 of the grated Mexican cheese blend. Repeat another layer in the same order: 2 torn tortillas, 1/3 of the sauce, remaining 1/2 of the chicken and onions, then top this second layer with 1/3 of the grated Mexican blend cheese. For the final layer, add remaining two torn tortilla pieces, cover with remaining sauce, then top it all off with the remaining grated cheese.
Bake the casserole (uncovered) in a 350° F. preheated oven for 20-25 minutes (mine was done in 20). The cheese and sauce should be bubbly when done. Remove chicken enchilada casserole from oven to a wire rack. Let the casserole rest for a minute or two to let the cheese firm up, so it will be easier to slice.
Slice the casserole into 6 pieces, and transfer to plates. Serve each piece with a dollop of sour cream and a cilantro leaf garnish, if desired. Enjoy!
Chicken Enchilada Mole Casserole https://www.thegratefulgirlcooks.com/chicken-enchilada-mole-casserole/