In a deep, heavy pot set over medium heat, sauté the onion and celery until soft, 7-8 minutes. Add the poblano peppers and garlic, sauté for 3-4 minutes. Add the flour and cook for a minutes to cook off the raw flour. Slowly add the stock, scraping up the browned bits from the bottom. Reduce to medium-low. Add milk, cream, half and half, corn, pepper flakes, chili powder; season to taste with salt and pepper. Cook until soup has reduced and thickened, 10-15 minutes. Remove half of the soup, puree in blender, and return to pot (or use an immersion blender, if you happen to have one). Add lobster or shrimp and allow to cook in the soup- 10 minutes for lobster, 5 minutes for shrimp. Take lobster out and roughly chop into bite sized pieces (shrimp are fine as-is). Stir in green onions, ladle into bowls, and garnish with cilantro.