Preheat oven to 350. Lightly grease 1 9x13 glass baking dish with non-stick cooking spray.
In a large mixing bowl, mix together the shredded chicken, sour cream, spinach, minced onion and garlic, cumin and some salt and pepper.
Lay 2 or 3 tortillas along the bottom of the pan. (I tore one in half to cover the 'gaps'.) Spoon half of the mixture over the tortillas and spread it thin. Add 2-3 more tortillas over the chicken mixture and then spoon the rest of the chicken mixture over that layer. Top with 2-3 more tortillas.
Then pour the green enchilada sauce over the top, Sprinkle the Mexican blend cheese over top.
Bake in the preheated oven for 30 minutes, or until cheese is melted and begins to golden, and sauce is bubbling.