Add stock to a large pot over medium-high heat and bring toa boil. Add carrot, celery, onion, and arborio. Boil 15 minutes then remove from heat. Season with salt.
In a large bowl, whisk together eggs and lemon juice. Continuing to whisk vigorously, slowly add a ladle of soup liquid into the egg mixture. Continue whisking and slowly add another 3-4 ladles of soup (one at a time) into the egg mixture.
Slowly stir egg mixture back into the soup. Stir in chicken.
Let the soup cool 5 minutes before serving.
