Cut poblano chiles and bell pepper in half lengthwise. Discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet. Flatten peppers with hand and broil 15 to 20 minutes or until roasted. Place peppers in a zip-top plastic bag and seal. Let stand 5 minutes. Peel and coarsely chop. Set aside. -
Cut kernels from ears of corn to measure 8 cups, reserving cobs; set kernels aside.
Combine reserved cobs and chicken broth in a large Dutch oven, and bring to a boil. Cover; reduce heat to mediumlow, and simmer 15 minutes. Remove and discard cobs.
Add 1 1/2 cups corn kernels to broth and bring to a boil. Cover; reduce heat, and simmer 10 minutes. Drain, reserving broth and kernels.
Meanwhile, melt butter in a large Dutch oven over low heat. Add onion, celery, and garlic; sauté over medium-high heat 5 minutes. Add reserved broth and remaining 6 1/2 cups uncooked corn kernels to pan; bring to a boil. Cover; reduce heat, and simmer 10 minutes. Stir in roasted peppers; cool slightly.
Place corn mixture in batches in a blender or food processor. Process until smooth, scraping sides of bowl.
Strain mixture, in batches, through a fine sieve, into a pan. Discard solids. Stir in reserved cooked 1 1/2 cups kernels, milk, cumin, salt, and pepper. Cook over medium heat 5 minutes or until thoroughly heated, stirring occasionally. Stir in cilantro. Sprinkle with red bell pepper, if desired.