1 cup chopped leeks, white and light green parts only (1 to 2 medium leeks)
1 medium carrot, peeled and sliced
1 bay leaf, broken in half
1 fresh thyme sprig or 1/2 teaspoon dried thyme
One 14 1/2-ounce can diced tomatoes and their juices
One 15-ounce can chickpeas, drained and rinsed
1 cup small, short dried pasta, such as tubetti, ditalini, or mini-penne
2 teaspoons chopped fresh rosemary
3 ounces (about 3 cups) baby spinach leaves
One 3- to 4-ounce piece of Parmesan cheese, preferably Parmigiano-Reggiano, at room temperature (so that it will be easy to shave)
Put the leeks, carrot, 2 teaspoons salt, bay leaf, thyme sprig or dried thyme, tomatoes, and 4 cups water in a medium, heavy pot set over high heat. Bring mixture to a boil, then reduce heat and simmer for 10 minutes. Strain stock into large bowl, pressing down on the vegetables to extract as much liquid as possible, and return stock to pot (discard vegetables in strainer). It should yield about 4 cups. If not, add enough water to equal this amount.
Purée 1/2 cup chickpeas with 1/4 cup water in a food processor or blender. Add the puréed chickpeas and remaining whole chickpeas, pasta, chopped rosemary, and 1 teaspoon salt to the strained stock. Bring mixture to a simmer and cook, stirring occasionally, until pasta is al dente, for 6 to 8 minutes or longer, according to package directions. (If the soup starts to cook down too much, add 1 to 1 1/2 cups additional water and return to simmer.) Add the spinach and cook 1 minute more or until wilted. Taste soup and season with salt, if needed.
To serve, ladle soup into 4 shallow soup bowls. Using a vegetable peeler, shave a generous amount of thin strips from the piece of Parmesan over each serving.
Cooking Tip: This soup is best made and served immediately; as it sits, the pasta will continue to absorb the liquids. If, however, you happen to have leftover soup that has become too thick, thin it with some additional water.