Cook onion and garlic in oil until onions are translucent.
Add in chicken broth.
In a bowl combine 1 cup water with 1/2 C masa harina. Mix until well blended and smooth.
Add into chicken broth and stir to combine.
Add in remaining 1 C water, enchilada sauce, green chilies, corn and tomatoes into chicken broth mixture.
Add in salt, chili powder and cumin.
Bring to a boil.
Add in chicken and reduce heat and allow to simmer for 30-40 minutes, until thickened.
If it thickens too much add some additional water or chicken broth.