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1
Bring 4 cups water to a boil.
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2
Place the dried mushrooms in a medium heatproof bowl; pour the boiling water over the mushrooms.
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3
Let stand until softened, about 20 minutes.
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4
Strain through a fine sieve into another bowl, reserving the liquid and mushrooms separately.
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5
Set aside.
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6
In a medium stockpot, heat the butter and oil over medium heat.
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7
Add the onion, and cook until caramelized, about 20 minutes, stirring occasionally.
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8
Add the reserved mushrooms along with the carrots, parsnips, and celery; cook, stirring often, until the vegetables are softened and fragrant, about 20 minutes.
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9
Stir the Swiss chard into the vegetable mixture in the pot.
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10
Add 3 1/2 quarts cold water, reserved mushroom liquid (being careful to leave behind any sediment), bay leaf, thyme, and parsley.
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11
Cover the pot, and bring to a boil; reduce heat, and simmer, uncovered, about 1 hour.
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12
Remove the pot from the heat, and strain the mixture through a fine sieve or cheesecloth-lined colander into a large heatproof bowl or saucepan, pressing down on the vegetables with the back of a wooden spoon to extract as much liquid as possible.
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13
Discard the solids.
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14
Store the stock in airtight containers in the refrigerator up to 3 days or in the freezer up to 6 months.
