Add oil to a large pot over medium heat. Add chicken breasts to pot and brown for 4-5 min per side. Set aside.
Add onions and garlic to pot and saute over medium heat for about 2 min or until onions begin to become translucent. Add chicken broth. Combine masa harina with 2 cups of water in a medium bowl and whisk until blended. Add masa mixture to pot with onions, garlic and broth. Add remaining water, enchilada sauce, cheese and spices to pot and bring mixture to a boil.
Shred the chicken into small, bite sized pieces and add it to the pot. Reduce heat and simmer soup for 30-40 min or until thick. Serve soup in cups or bowls and garnish with shredded cheddar cheese crumbled corn tortilla chips, sour cream.