Preheat oven to 350°. Spray a 9 x 13" casserole dish with nonstick spray.
Arrange the tortillas in a single layer in the casserole dish.
Make the Enchilada Sauce:
Melt the butter in a medium pot. Whisk in the flour and make sure there aren't any clumps.
Add the chili powder, cumin, and tomato sauce and whisk to combine.
Add the chicken broth and bring to a boil. Whisk until the sauce thickens, remove from heat and set aside.
Make the Shredded Chicken:
Heat the oil in a large pot or saucepan. Add the chicken thighs, season with salt, pepper, and chili powder. Sauté for 1-2 minutes. Flip and season the other side. Cover the thighs with chicken broth and bring to a boil. Boil until the chicken is cooked through and no longer pink in the center.
Remove the chicken from the pot and use two forks to shred the chicken by pulling apart in opposite directions.
Assemble and Bake:
Add a generous spoonful (about ¼ - ½ cup) of the enchilada sauce to each of the tortillas.
Add the shredded chicken and black beans evenly to the tortillas. Add about 1-2 tablespoons of the shredded cheese.
Close the tortillas and spread the top with remaining sauce. Sprinkle with remaining cheese.