Cheesy Chicken Enchilada Soup

I have been searching for a good enchilada soup since we moved back to AZ, mainly because I had a great one at both Chili's and Zoupa and became somewhat obsessed.  So I got on Pinterest and began my search landing on this one.  It's actual name is 20 - minute cheesy...I found it did go together rather quickly, especially since I always keep 2-cup bags of cooked chicken in the freezer.  I think I might even try it with the homemade enchilada sauce she talked about.
Makes: 6-8 servings (I can only double this in my pan)

2 Tblsp. oil
1 c. diced onion
2 cloves garlic, minced
1/2 c. masa harina
4 c. or 1 (32 oz. box) chicken stock
2 c. cooked, shredded chicken
1  (16 oz. can) red enchilada sauce (Macayo is the one I like) or homemade
2 (14 oz. cans) black beans, rinsed and drained
1 (14 oz. can) diced tomatoes, with juices (she prefers fire-roasted)
1 (4 oz. can) chopped green chilies
1/2 tsp. ground cumin
8 oz. sharp cheddar cheese or pepper jack for a little more kick
1 tsp. salt, or more/less to taste
optional toppings: tortilla chips/strips, diced/sliced avocado, grated cheese, sour cream, chopped
fresh cilantro, and/or pico de gallo

Heat the oil in a large stock over medium-high heat. Add the onion and saute for 5 minutes, or until cooked and translucent.  Add the garlic and saute for an additional minute until fragrant.  Stir in the masa harina and cook for an additional minute.
Pour in half of the chicken stock, and stir until completely combined.  Add in the remainder of the chicken stock, and stir to combine.  Immediately add in the chicken, enchilada sauce, black beans, tomatoes, green chiles, salt and cumin, and stir until combined.  Continue stirring occasionally until the mixture reaches a simmer.  Reduce heat to medium-low and let it simmer for 3 minutes, stirring occasionally so that the soup does not stick to the bottom of the pan.  Then stir in the cheese, one handful at a time, until combined.  Taste, and season the soup to taste with salt.
Serve the soup warm with desired toppings.