In a large pot, combine the chicken broth, fresh lemon juice, shredded carrots, finely chopped onion, and finely chopped celery. Add in the chicken soup base and ground white pepper for seasoning. Bring the mixture to a boil over medium-high heat, then reduce to a simmer. Let it cook for 15-20 minutes, until the vegetables are tender and aromatic.

While the soup is simmering, take a small bowl and blend the margarine with the all-purpose flour to form a smooth paste. Gradually stir this paste into the simmering soup, ensuring it dissolves fully. Continue to simmer and stir the soup for 8-10 minutes, until it thickens to a velvety consistency that clings to a spoon.

In a separate bowl, beat the egg yolks until they turn a pale color. Slowly whisk in a few ladles of the hot soup to temper the eggs, which prevents curdling. Once combined, return the egg mixture to the pot. Stir constantly while gently heating the soup through—avoid boiling to maintain that creamy texture you desire in your Greek Lemon Chicken Soup.

Mix in the cooked white rice and diced cooked chicken, allowing them to warm through on low heat. Stir periodically to ensure even distribution and prevent sticking. This step adds heartiness and flavor, making every spoonful of your Greek Lemon Chicken Soup substantial and satisfying.

Ladle the warm and inviting soup into bowls, garnishing each serving with fresh lemon slices for a pop of color and tang. This final touch not only elevates the presentation but also enhances the zesty aroma, inviting family and friends to savor this comforting dish.