In a saucepot, arrange the chicken in a single layer. Add water, quartered onions, smashed garlic cloves, ginger, salt, and peppercorns.
Bring to a boil, skimming scum that floats on top. Lower heat, cover, and cook in barely a simmer for about 15 minutes or until thermometer inserted in the thickest part of chicken reads 165 F.
With a slotted spoon, remove chicken from pot and allow to cool to touch. Coarsely shred chicken and keep warm. Discard bones.
Using a fine-mesh sieve, strain liquid. Discard aromatics and reserve 4 cups of the broth.
In a large bowl, stand an ear of corn up and using a small knife, thinly cut the kernels off from top to bottom. Rotate the corn when done with each section to get to the next. Scrape the sides of the cobs using a spoon to extract the remaining pulp and milky juice.
Add corn and soy sauce to the pot. Cook for medium heat for about 8 to 10 minutes or until tender.
Add chicken.
In a small bowl, combine 3 teaspoons of the cornstarch with ¼ cup water. Stir until dissolved and smooth.
Add cornstarch slurry to the pot, whisking vigorously to prevent lumps. Continue to whisk until the mixture begins to thicken. Lower heat to a gentle simmer.
In a bowl, combine eggs and the remaining 1 teaspoon cornstarch. Whisk together until smooth.
Slowly drizzle the egg mixture into the soup and let stand for 15 seconds and then stir gently stir to break up.
Season the soup with salt and pepper to taste.
Ladle soup into servings bowls and sprinkle with green onions. Serve hot.