Remove silk from corn ears and roast the corn in their husks for 35 minutes in a 350 F oven.
Chill corn and cut from the cob, reserve.
Poach chicken in stock until cooked through (165 degrees internal temperature for 15 seconds), reserve
stock. Dice chicken and set aside until needed.
In a large pot, saute onions, celery and garlic in oil until slightly soft. Add flour to make roux, stir.
Add chicken stock, stir to dissolve roux, simmer for 5 minutes.
Add diced potatoes and simmer until potatoes are tender, about 15 minutes.
Add chicken and milk to soup, return to a simmer, do not boil.
Add cilantro, adjust seasoning.