Simmering ears of corn in broth enhances the soup’s sweet flavor. (When using frozen corn, skip this step.) To add more “heat,” double the number of green chilies.
Using tongs, hold chile directly over flame of gas burner, turning frequently, until entire surface is blistered. (Alternatively, roast chile under broiler.) Place roasted chile in medium bowl. Cover with plate and let steam 20 minutes. (Alternatively, place chile in small paper bag. Close securely and let steam.) When cool enough to handle, peel off charred skin and discard. Remove and discard seeds. Finely chop chile flesh; set aside.
Using a sharp knife, cut corn off cobs; reserve cobs. Heat small cast-iron or other heavy skillet over medium heat. Add corn and cook, stirring occasionally, until well browned, 10 to 12 minutes. Set aside.
Break reserved cobs in half. In large saucepan, combine broth and cobs. Bring to a boil. Reduce heat, cover and simmer 15 minutes. Discard cobs.
In food processor or blender, combine reserved corn kernels and broth and process, in batches if necessary, until very smooth. Strain through fine-mesh sieve back into saucepan, using a rubber spatula to press mixture through mesh. Stir in tofu, reserved chopped chile, and salt and pepper to taste. Rewarm over low heat, stirring occasionally.
Ladle soup into bowls and garnish each serving with cilantro. Serve with lime wedges if desired.