Preheat the oven to 350°F (175°C). Lightly spray a 10–12 inch ovenproof skillet or baking dish with cooking spray.
Arrange 5 tortillas in the bottom of the skillet or dish, overlapping to fully cover the base.
Spread half of the shredded chicken evenly over the tortillas.
Spoon half of the salsa verde over the chicken, then scatter half of the black beans and half of the corn on top.
Sprinkle 1½ cups of the shredded Mexican blend cheese over the layer.
Repeat the layers: place the remaining 5 tortillas, then the remaining chicken, salsa verde, black beans, corn, and finish with the remaining 1½ cups cheese, ensuring salsa covers the tortillas.
Bake in the preheated oven for 20–30 minutes, until the cheese is melted and the casserole is heated through.
Remove from the oven, top with sliced green onions, slice into triangles, and serve with desired toppings.