Actually the way I've always made it was just a simple bechemal sauce
(white sauce - butter/flour/milk) thinned out with stock (chicken
and/or vegetable), add corn and be done with it . Some ground
nutmeg, salt/pepper, and then season w/whatever else desired, e.g.
cayenne. This is very good with canned (gasp!) generic green chiles,
but a nice flavor results. Could use any other mild chile I think
although I would probably cook them down first with some onion, then
puree and add to the soup (or don't puree - preference dictates).
I think if one roasted the corn briefly with fresh chiles and onion,
it would be wonderful.