Using a pan on the stove, melt butter over medium heat and stir in flour and cook until colour starts browning

Add broth and whisk until combined and smooth. Continue cooking until thick and bubbling.

Turn down the heat to medium-low and stir in the chilies and sour cream. Cook for one minute and set aside

In a bowl combine the chicken, diced onion and 1 1/2 cups of the shredded cheese

Scoop 1 cup of the sauce into a greased baking dish {I used smaller baking dishes, so I did this between two}. 

Using a large serving spoon, scoop some of the mixture onto each tortilla and roll, and place side by side into a baking dish, seams down. I just guessed how much to use for each, to use up all of the chicken mixture

Pour remaining sauce over the tortilla rolls, then top with remaining cheese

Bake at 350 for 20-25 minutes then broil to brown the tops if preferred. Once baking is complete, let stand for about 5 minutes to allow sauce to settle and self-thicken up. Top with chopped cilantro for garnish if you so wish - and enjoy!