serves: makes 4 quarts of soup base
This versatile soup base is not truly a broth, in the way my turkey broth is-that is, a clear liquid strained of all the ingredients that gave it flavor. In truth the base starts cooking with several pounds of potatoes, carrots and celery and they stay in there. Yet remarkably it ends up light, clear and clean tasting, and the word broth seems to fit.
¼ cup extra-virgin olive oil
2½ pounds russet potatoes, peeled and dices into 1/2-inch cubes
2 tablespoons salt
2 stalks celery , finely chopped
2 medium carrots, peeled and grated
3 tablespoons tomato paste
3 whole bay leaves
2 pieces outer rind of Grana Padano, 2 or 3-inch square, rinsed
4 quarts water, heated to boil
¼ teaspoon freshly ground black pepper, or more to taste
Pour the oil into the pot and set over medium-high heat. Let the oil get quite hot, but not smoking. Dump in the potatoes, sprinkle on 1 teaspoon of the salt, and toss them in the oil until well-coated. Cook them for 6 minutes or more, until lightly crusted and caramelized without taking on any color. Lower the heat to prevent burning and alternately stir the potatoes. When the potatoes are leaving a crust on the pan bottom (about 3-5 minutes), toss in the celery and carrots. Stir up everything well scraping up any potato crust, raise the heat a bit and cook, for 2 or 3 minutes, until all the vegetables are hot and steaming. Push them aside to clear the pan bottom in the center and drop in the tomato paste. Toast it in the hot spot for a minute or 2, stirring, then work the paste into the vegetables.
Pour the gallon of hot water into the pan, drop in the bay leaves and pieces of cheese rind, grind in 1/4 teaspoon or more of black pepper, add another teaspoon of salt and stir well. Cover the pot and bring the broth to a boil, adjusting the heat to keep a steady but not violent bubbling and let cook for an hour, covered. Stir occasionally. Uncover the pot and cook the broth for another hour or so, still at a low bubbling boil, until it has reduced to 4 quarts. (If you're in a hurry, raise the heat and concentrate the broth quickly; stir now and then to prevent burning.) Remove the bay leaves but leave the cheese rind, whole or chopped up, for those who like it.
You can use the broth right away, or any part of it, for the finished soups that follow. Or let it cool and pack it in measured containers. Keep it refrigerated for 3 or 4 days or frozen, in filled and tightly sealed containers, for 4 to 6 months.