
Sauté the veggies. Heat the oil in a large stockpot over medium-high heat. Add the onion and sauté for 5 minutes, stirring occasionally. Add the garlic and sauté for 1 minute, stirring frequently.
Simmer. Add the chicken stock, cooked chicken, enchilada sauce, black beans, tomatoes, green chiles, cumin and stir to combine. Continue cooking the soup until it reaches a simmer, then reduce heat to medium-low to maintain the simmer.
Mix in the masa harina. Ladle out 2 cups of the hot broth into a heatproof bowl or measuring cup. Add the masa harina and whisk until combined. Add the mixture back to the hot soup and stir until combined.
Add the cheeses. Add the cheeses and stir until melted and evenly combined. Taste and season the soup with salt and pepper as needed.
Serve. Serve warm, garnished with lots of your favorite toppings.