Stock - Homemade Vegetable

In a medium stockpot over medium-high heat, melt butter and olive oil. Add onion, and cook, stirring, until caramelized, about 8 minutes. Add carrots, parsnips, and celery; cook until tender, about 15 minutes. Wash and drain chard thoroughly. Chop into 1-inch pieces. Add to the vegetable mixture. Then add 3 quarts plus 2 cups cold water, thyme, parsley, and bay leaf. Bring to a boil, reduce heat, and let simmer about 1 hour; liquid should be highly flavored. Remove from heat, and strain stock through a fine sieve, pressing on vegetables to extract juices. Discard vegetables. Stock can be refrigerated for 3 to 4 days or frozen for up to 3 months.