In a large pot, combine 8 cups of chicken broth, 1/2 cup of fresh lemon juice, 1 cup of shredded carrots, 1 finely chopped onion, and 1/2 cup of finely chopped celery. Add 2 tablespoons of chicken soup base and 1/2 teaspoon of ground white pepper. Bring the mixture to a rolling boil over medium-high heat, then reduce to a simmer for 15-20 minutes, or until the vegetables are tender and fragrant.

While the soup is simmering, in a small bowl, mix together 2 tablespoons of margarine and 1/4 cup of all-purpose flour until a smooth paste forms. Gradually add this mixture to the simmering pot, stirring constantly with a whisk. Continue stirring for about 8-10 minutes until the soup thickens slightly.

In a separate bowl, beat 3 egg yolks until they turn pale in color. Carefully ladle about 1 cup of the hot soup into the yolks, whisking continuously to temper them. Once mixed, slowly pour the tempered yolk mixture back into the pot, stirring gently to combine.

Stir in 1 cup of cooked white rice and 2 cups of diced cooked chicken into the hot soup, mixing thoroughly. Continue warming the soup over low heat for about 5 minutes.

Ladle the soup into warm bowls and garnish with fresh lemon slices for a delightful touch.