*In medium pot, bring chicken stock and tinned tomatoes to a boil -- turn down and let simmer covered.
In a large skillet, heat butter and oil. Add onions and brown for approx 3-4 minutes. Add chicken to brown. Add chilies and spices and stir to incorporate. Add ap flour and slowly add milk, stirring to incorporate.
Let cook for a few minutes until thickened and flour has been incorporated into sauce.
Ladle 1 cup of broth/tomato combo into the skillet and stir to thin a bit. Pour entire contents into soup pot and bring to a bare simmer, simmering for about 10 minutes.
Stir in cheese, corn and creme fraiche slowly incorporating so both combine into the broth.
Serve with chopped cilantro and tortilla chips, tobasco, rice etc. Texture of the soup should be velvety.not thick