Mix 2 tablespoons butter and flour in small bowl to blend; set aside.
Finely chop onion and celery in processor. Melt 2 tablespoons butter in large pot over medium-high heat. Add onion-celery mixture and chilies; sauté until soft, about 6 minutes. Add creamed corn and next 5 ingredients; bring to boil. Reduce heat. Whisk in butter-flour mixture and simmer 15 minutes to blend flavors. Add shrimp and 4 tablespoons cilantro; simmer until shrimp are cooked through, about 5 minutes longer. Season with salt and pepper.
Ladle chowder into bowls. Sprinkle with remaining 2 tablespoons cilantro.
Fresh green chilies, often called pasillas; available at Latin American markets and some supermarkets.
