Meanwhile, in large bowl, with wire whisk, mix eggs and lemon juice until combined. Slowly whisk 2 cups simmering broth into bowl with egg mixture, whisking constantly. Return broth mixture to saucepan; heat just to simmering, whisking constantly, about 5 minutes (do not boil or soup will curdle). Stir in shredded chicken and margarine or butter. Sprinkle with chopped chives to serve if you like. Makes about 7 cups or 6 first-course servings.