Feel free to use the onion skins, they'll add flavor and a lovely caramel color to the stock. If parsnips are available, you can sub out some of the carrots with chopped parsnips for more flavor.
- 1 ounce dried mushrooms*
- 4 Tbsp olive oil
- 4 cups chopped onion
- 2 cups chopped celery
- 3 cups chopped carrot
- 1 cup chopped fennel bulb (optional)
- 2 large garlic cloves, smashed (can leave skins on)
- 2 Tbsp tomato paste
- 1 Tbsp fresh rosemary
- 2 teaspoons dried thyme
- 1 teaspoon black peppercorns
- 4 bay leaves
- 1/2 cup chopped parsley
*If you want to use fresh mushrooms instead, use about 5-6 ounces, thickly slice them, and dry sauté them first in a separate pan, until they are lightly browned and have given up some of their moisture. Then add in with the rest of the vegetables.
1 Place the dried mushrooms in a large bowl and pour 1 quart of boiling water over them. Set aside.
2 Heat the olive oil over high heat in a large stockpot. Add the chopped onions, celery, carrots, and fennel (if using) and stir to coat. Sprinkle with salt. Cook over high heat for several minutes, stirring only occasionally. Given that there are so many vegetables, and they have a high moisture content, it may take more heat and longer time to brown than you would expect. Cook until the vegetables begin to brown.
3 Add the garlic and tomato paste and stir to combine.Cook, stirring often, for 2-3 minutes, or until the tomato paste begins to turn a rusty color. Add the mushrooms and their soaking water, the rosemary, thyme, onion skins if using, peppercorns, bay leaves, parsley and 4 additional quarts of water. Bring to a simmer and then drop the heat until you just get a bare simmer. The surface of the stock should just barely be bubbling. Cook for 1 1/2 hours.
4 Using a spider skimmer or slotted spoon, remove all the big pieces of vegetable and mushroom. Discard or compost. Set up a large bowl or pot with a sieve set over it. Line the sieve with a paper towel and pour the stock through it. When you have about half the stock poured through, stop, let what's in the strainer filter through, and change the paper towel; the old one will be gunked up with debris. Filter the rest of the stock.
To store, pour into glass jars and refrigerate for up to a week, or freeze. If you freeze in glass jars, leave at least an inch and a half of headroom so the stock can expand without breaking the glass of the jar.