Step 1

In a large saucepan over medium-high heat, bring the stock to a boil. Reduce the heat to medium-low and add the orzo, salt, pepper, and sugar. Cook, stirring occasionally, for about 8 minutes, until al dente. Reserve 2 cups of the stock.

Step 2

In a medium bowl, using an electric mixer on medium speed, beat the egg whites until soft peaks form. (You can do this by hand or with a stand mixer too.) Beat in the egg yolks and lemon juice until combined. Slowly pour 2 cups of the reserved hot stock into the egg mixture, whisking continuously, until incorporated.

Step 3

Return the soup to medium-low heat and whisk in the lemon-egg mixture. Simmer for about 20 minutes, until thickened slightly.

Step 4

Ladle the soup into warm bowls. Garnish with white pepper, chopped dill, a dill sprig, and lemon slices.