Heat 1 TBS butter in skillet and add chopped onion. Cook over low heat until soft. Put cooked onions, corn cut from cob and cornstarch mixed with water into food processor. Process until smooth. Heat remaining 2 TBS butter in large saucepan and add corn puree. Stir constantly over medium heat until thick. Whisk in milk, reduce heat to low and simmer 15 minutes, stirring frequently. Stir in diced chiles and cream. Continue to simmer for 10 minutes. Remove from heat, chill and serve garnished with crumbled feta cheese.
*Peppers can be roasted in 375 degree oven, on foil, for 14 minutes, turned 180 degrees and roasted an additional 14 minutes. Remove from oven and completely cover in foil. Let cool to room temperature, then peel, seed and dice.