makes 8 cups
12 cups cold water
1 tablespoon whole black peppercorns
3 carrots, unpeeled and halved crosswise
1 yellow onion, unpeeled and halved lengthwise
1 small fennel bulb with stalks, bulb halved and stalks halved crosswise
6 ounces fresh whole shiitake mushrooms (about 10 whole mushrooms)
2 celery stalks, halved crosswise
1 large garlic head, halved crosswise
8 fresh parsley sprigs
6 thyme sprigs
3 fresh bay leaves
1 (3-ounce) Parmesan cheese rind (optional)
2 teaspoons kosher salt (optional)
Place water, black peppercorns, carrots, onion, fennel, mushrooms, celery, garlic, parsley, thyme, bay leaves, and Parmesan rind (if using) in a large stockpot. Bring to a gentle boil over medium, and boil, uncovered, for 30 to 40 minutes. Reduce heat to low; simmer, uncovered, until stock is rich and fragrant, about 45 minutes.
Drain stock through a fine mesh strainer into a large (3 quart) heatproof container; discard solids. Add salt (if using), or leave stock unseasoned to use in recipes. Let stock cool, uncovered, at room temperature for 1 hour. Cover and transfer to refrigerator until completely chilled. Refrigerated stock will keep for about 1 week.