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, 1 finely chopped celery stalk, 2 tablespoons of chicken soup base, and 1/2 teaspoon of ground white pepper. Bring this mixture to a boil over medium-high heat, then reduce to a simmer for 15-20 minutes, allowing the vegetables to soften and their flavors to meld beautifully.

While the soup simmers, prepare a thickening paste by melting 4 tablespoons of margarine in a small bowl and whisking in 4 tablespoons of all-purpose flour until smooth. Gradually stir this paste into the simmering soup, cooking it for about 8-10 minutes on low heat.

In a separate bowl, beat 3 egg yolks until smooth and creamy. Slowly whisk in a ladleful of the hot soup to temper the yolks, then carefully stir it back into the pot of soup.

Add 1 cup of cooked white rice and 2 cups of diced cooked chicken. Gently heat through on low for about 5 minutes.

Ladle the soup into warm bowls, garnishing with fresh lemon slices before serving.