1In a large pot over medium heat, cook chicken breasts in oil until well browned on all sides. Remove and set aside.
2Cook onion and garlic in remaining oil until onions are translucent. Pour in chicken broth.
3In a bowl, whisk together masa harina and half of water until well blended. Pour into pot with remaining water, enchilada sauce, Cheddar, salt, chilli powder and cumin. Bring to a boil.
4Shred cooked chicken and add it to the pot. Reduce heat and simmer 30 to 40 minutes, until thickened.
5Garnish with more Cheddar cheese and fresh chillies.