I found this recipe while looking for something else.
Horn & Hardart Chicken Soup
"The Book of Lost Recipes: The Best Signature Dishes from Historic Restaurants Rediscovered"
by Jaya Saxena
From: "The Robert F. Byrnes collection of Automat Memorabilia, Manuscripts and Archives Division,"
at The New York Public Library
3/4 cup white rice
3 tbsp butter
1/2 lb chicken thighs, chopped
2 egg yolks
1 gal. chicken stock
3 tbsp cornstarch
2 tbsp salt
Dash white pepper
Cook the rice until done, and set aside. Heat the butter
in the bottom of a large stockpot over medium heat. Add
the chopped chicken meat and cook until almost done, about
8 minutes. Meanwhile, beat the egg yolks into the stock
until fully incorporated. When the chicken is done, add
the stock mixture and rice to the pot.Dissolve the cornstarch
in a little water and add to the stock with the rest of the
seasonings. Bring to a boil and simmer for 10 minutes. Check
seasoning and serve hot.