Spinach, Leek, and Potato Soup

Cooking time: 30 minutes. The famous vichissoise, but without cream and with spinach, giving it a beautiful bright green hue and useful for your waistline.
Slice the leeks crosswise and dip them in a large bowl of water to wash off the dirt; drain in a colander, leaving the dirt out, and rinse again in fresh water if necessary. In a large saucepan over medium-high heat, melt the butter. Add the leeks and salt and cook until soft, stirring frequently, about 5 minutes. Add the broth and potatoes. Bring to a simmer, covered; reduce heat and simmer until potatoes are tender after piercing, 10-15 minutes. Add the spinach and cook until wilted, about 1 minute.Whisk the puree in a blender, if necessary in portions, holding the lid with a towel. Pour back into the pan and, if desired, dilute with the broth; reheat until hot. Season with salt and pepper. Divide the soup into 4 serving plates and top each with about 1/4 cup of croutons.Note: A nutritional analysis is provided for each serving.