To make an egg-drop version of this soup, beat two eggs in a bowl and slowly drizzle them into the simmering broth just before serving.
In a pot, bring broth and 2 cups water to a boil. Meanwhile, slice corn from cobs and set aside; add cobs to pot. Remove and discard shiitake stems; cut caps in half (into quarters, if large) and add to pot. Thinly slice scallions and add white and light-green parts to pot, reserving dark-green tops. Grate ginger directly into pot. Reduce heat to low; simmer 10 minutes.
Remove cobs from pot. Add corn kernels and tofu. Stir, breaking tofu into bite-size pieces; simmer 1 minute. Stir in soy sauce, sambal oelek, and oil. Serve, with scallion tops, drizzled with more sambal oelek and oil.