Preheat oven to 350° F. Spray a 9 x 13 pan and 8 x 8 pan with non-stick pan spray.

In a large bowl mix together the shredded chicken, chopped onion, spinach, 2 Tbsp. cilantro, and shredded Monterey Jack cheese, reserving about 2 c. for the topping.

Heat 2 Tbsp. olive oil over medium heat. Add the 2 Tbsp. flour to the hot oil and stir till all the flour is moistened. Add chicken broth all at once. Cook over medium heat till thickened, about 3-4 minutes, stirring constantly. Mix in Greek yogurt and tomatillo sauce.

Using a hand blender, blend until smooth. Keep sauce warm over very low heat, stirring frequently.

Build enchiladas by warming the tortillas slightly so they roll more easily. I usually put them between sheets of paper towel and warm the stack in the microwave for 30 seconds.

Build enchiladas by scooping 1/4-1/3 c. filling in each tortilla. Fold one end just over the middle and continue rolling to form the enchilada. Place in the prepared pan after rolling. Eight enchiladas fit in the 9 x 13 pan and 5 enchiladas fit in the 8 x 8 pan.

Pour tomatillo sauce evenly over prepared enchiladas. Sprinkle remaining cheese proportionately on each pan of enchiladas.

Bake at 350° F for about 30 minutes or until bubbly and heated through. Serve with shredded lettuce, chopped tomatoes, sliced avocado, and chopped fresh cilantro.