Heat the butter in a Dutch oven over medium-high heat and saute the onion until tender, about 7 minutes. Add the garlic and saute for another minute.
Add the masa harina and flour and stir to combine. Cook for 1 minute. Gradually add the broth, whisking constantly to prevent clumping. Add the evaporated milk and simmer until slightly thickened.
Add the shredded chicken, salsa, corn, beans, and all the spices. Stir to combine, bring to a boil, reduce the heat to low, cover and simmer for 15 minutes, stirring frequently. Add the shredded cheese, sour cream, and cilantro, stir to combine and warm through for another minute. Add salt and pepper to taste.
Serve hot topped with sour cream, shredded cheddar cheese, chopped fresh cilantro and crumbled tortilla chips.
Note: Leftovers will be thicker when reheated. Add some extra chicken broth or milk accordingly.