Lemon Chicken and Orzo Soup

Name: Lemon Chicken and Orzo Soup
Yield: Serves 4
Ingredients: 2 tablespoons, unsalted butter; 1 , small onion, chopped fine; 8 cups, chicken broth; 2 sprigs, fresh thyme; , Salt and pepper; 1 cup, orzo; 6 , large egg yolks; 6 tablespoons, lemon juice (2 lemons); 2 cups shredded, rotisserie chicken; 2 tablespoons, chopped fresh chives