MAKES ABOUT 2½ QUARTS
- ¼ cup extra-virgin olive oil, plus more for drizzling
- 1 medium onion, chopped
- 1 large carrot, peeled and chopped
- 4 celery stalks, chopped
- ¼ cup tomato paste
- 2 fresh bay leaves
- 1 tablespoon chopped fresh thyme
- ½ teaspoon crushed red pepper flakes
- 4 teaspoons kosher salt
- 1 large head cauliflower, cut into 1-inch pieces, including the tender leaves
- 1½ cups long-grain rice
- ½ cup chopped fresh Italian parsley
- Freshly grated Grana Padano, for serving
To a large Dutch oven over medium heat, add the olive oil. When the oil is hot, add the onion, carrot, and celery. Cook until the vegetables begin to soften, about 5 minutes. Clear a space in the pan and add the tomato paste. Cook and stir the tomato paste in that spot until it is toasted and darkens a shade or two, about 2 to 3 minutes. Add 5 quarts cold water, the bay leaves, thyme, crushed red pepper, and salt. Bring to a boil, and simmer rapidly, uncovered, until vegetables are tender, about 30 minutes.
Add the cauliflower, cover, and cook until the cauliflower is very tender, about 30 minutes.
Add the rice. Uncover and simmer rapidly until the soup is thickened and the rice is just tender, about 15 minutes. (If you are not going to serve all of the soup at once, just cook the rice in the amount of soup you want to serve, and cut the rice proportionally.)
Remove bay leaves. Add the parsley, and serve soup with a drizzle of olive oil and a sprinkle of grated cheese.