In a large soup pot, bring chicken broth to a boil. Add rice, salt and pepper and simmer until rice is tender, about 15 minutes.
Remove one cup of the broth from the pot and pour into a medium bowl. Add corn starch and whisk until dissolved. Pour in lemon juice and whisk once more.
To temper the eggs, slowly add the whisked eggs to the broth/cornstarch/lemon juice mixture. Whisk constantly so that the eggs gradually come to temperature. Continue until all of the eggs are fully incorporated.
Pour the warmed egg/broth mixture back into the large soup pot and stir until mixture begins to thicken, about 5 minutes.
Add shredded chicken breasts and cook until heated through. Check for seasoning and adjust accordingly. Serve with sliced scallions if you wish.