Ingredients

• 2 tablespoons cornstarch
• 1 cup water
• 3 cups low-sodium low-fat chicken broth (24 fl oz)
• 2 teaspoons finely grated fresh lemon zest
• 1/2 teaspoon salt
• 1 large egg, lightly beaten
• 1 cup firmly packed shredded spinach leaves

Instructions

1. Stir together cornstarch and 1/4 cup water until smooth.
2. Bring broth and remaining 3/4 cup water to a boil in a 2- to 3-quart heavy saucepan over high heat, then reduce heat to moderately high and add zest and salt.
3. Stir cornstarch mixture and add to soup, whisking until smooth. Simmer, whisking, 2 minutes, then add egg in a slow stream, stirring with a spoon. Stir in spinach and return to a boil, then remove from heat. Season with salt.