Adjust oven racks to upper-middle and lower-middle positions and preheat oven to 450º. Lay tortillas on two baking sheets and lightly spray both sides with vegetable oil spay. Bake until lightly crisped and browned, rotating halfway, about 12 minutes. Let cool slightly and then break into pieces and set aside.
Meanwhile, melt butter in large Dutch oven over medium-high heat. Add onions, minced jalapeños and cumin, and cook until lightly browned, about 8 minutes. Stir in tomatoes/chiles and their juices and cook until most of the liquid is gone, about 10 - 12 minutes.
Add flour and cook and stir for 1 minute. Slowly stir in broth and then cream, bring to a simmer and cook until thickened, about 2 - 3 minutes. Season with salt and pepper, to taste. Carefully add chicken and stir and cook until no longer pink, about 5 minutes ~ chicken should be slightly underdone. Remove from heat, gradually add cheese and cilantro, stir until cheese is melted.
Place half of tortilla pieces in bottom of 9" X 13" baking dish set on a baking sheet. Spoon half of mixture over chips. Scatter remaining tortilla pieces over filling, then top with remaining filling.
Bake casserole on lower rack until bubbly, about 15 minutes. Sprinkle with crushed corn chips and bake until lightly browned, about 10 minutes. Let casserole cool for 10 - 15 minutes before serving.