This light soup is made creamy by pureeing the leeks and potatoes, not by adding any dairy. The ginger is a surprise, adding a pleasant zing to the mix, while the bright orange swirl of pureed carrot atop each serving adds both color and flavor.
In a 3- or 4-quart saucepan or saucier, combine 4 cups of the broth, the leeks, carrots, potatoes, ginger, tomato paste, garlic, and ½ teaspoon salt, and bring to a boil over high heat. Adjust the heat to a simmer, cover, and cook for 25 minutes, or until the vegetables are very tender. Let cool slightly, then lift the carrots from the pan using a slotted spoon and set aside.
Process the soup directly in the pot until very smooth, with an immersion blender. Alternatively, working in batches, transfer to a stand blender or food processor and process until very smooth. Add a small amount of the remaining broth to thin the soup to preferred consistency, and then return to the saucepan.
Place the curry in a small saucepan over low heat for 1 minute. Add the reserved carrot pieces and ½ cup of the remaining chicken broth and simmer for 3 minutes. Remove form the heat. Puree the carrot mixture with an immersion blender. Or, puree the mixture in a stand blender or food processor. Taste and adjust the seasoning with salt.
Reheat the soup and season to taste with salt and pepper. Ladle the soup into bowls, and swirl a spoonful of the carrot puree in the center of each bowl. Garnish with the cilantro leaves and serve hot.
