In large stock pot, sweat onion in oil until tender. Add garlic, chicken, broth, enchilada sauce, cheese and seasonings. Amounts of seasonings are approximate based on the blend in your enchilada sauce and your particular preferences. In a bowl, whisk together masa harina with 2 cups water until well blended. Pour into pot with remaining water. Bring to a boil. Bring to a simmer and cover for 30-40 min. Optional garnish with crispy tortilla strips and sour cream.