In a large skillet heat olive oil over medium-high heat. Add onion, red bell pepper and banana peppers. Season with the crushed red pepper flakes and salt and pepper. Saute until veggies have softened, 6-8 minutes.
Add the garlic and saute for another minute or two. Sprinkle the flour over the veggies and stir to combine. Cook while stirring for several minutes so that the flour loses its raw taste.
Whisk in the chicken broth and stir until bubbly and smooth. Add the baby spinach and continue cooking for another minute or two or until spinach has wilted. Stir in the cooked chicken and cannellini beans and remove from heat.
Spray a large skillet or griddle with cooking spray. Heat over medium to medium-high heat. Place one tortilla on griddle and spread 1/4 cup cheese over tortilla.
Spread chicken, bean and spinach mixture over one half of the tortilla.
Check underside of tortilla and when browned a bit, flip the half with just cheese over the half with the chicken.
Remove from heat and cut into slices. Top with diced avocado and sour cream, if desired.