Don't bother peeling the onions; their skins add a nice, rich brown color to this vegetable stock. If you'd like, remove the skins for use in dishes when a lighter color is preferred, such as in risotto or cream sauces.
Ingredients
1 tablespoon olive oil
2 medium onions, unpeeled, cut into 1" pieces
10 celery stalks, cut into 1" pieces
2 large carrots, peeled, cut into 1" pieces
8 ounces crimini (baby bella) or button mushrooms, halved if large
1 small fennel bulb, cut into 1" pieces
1 head of garlic, halved crosswise
6 sprigs flat-leaf parsley
1 bay leaf
1 teaspoon whole black peppercorns
Directions
Heat oil in a large stockpot over medium-high heat. Add remaining ingredients and cook, stirring occasionally, until vegetables begin to soften, 5-7 minutes. Add 4 quarts cold water. Bring to a boil; reduce heat and simmer until stock is reduced by half, 1-1 1/2 hours.
Strain stock through a fine-mesh sieve into a large bowl; discard solids. DO AHEAD: Stock can be made 3 days ahead. Let cool completely, then cover and chill, or freeze for up to 3 months.
