Dice the onion and mince the garlic. Open all canned goods.
Add the oil to a large stockpot or dutch oven. Heat on medium/high heat and toss in the chopped onion. Sauté until translucent, about 5-6 minutes, then add garlic and heat for an additional minute.
Stir in the masa harina and cook for another minute.
Pour in 1 & ½ C. of chicken stock and whisk until lumps are gone.
Add the remaining cup and a half of chicken stock and whisk until combined.
Add the shredded chicken, enchilada sauce, black beans, diced tomatoes, and green chiles. Stir until well combined, then add salt and cumin. Mix until blended.
Let the mixture simmer on medium/low heat for about 3-5 minutes, stirring continuously to prevent sticking.
Remove from heat and add in the cheese, stirring until blended and melted.
Serve immediately, topped with optional toppings if desired.