Ingredients

1 tablespoon butter 

1 tablespoon olive oil 

1 onion (about 1/2 pound), coarsely chopped 

2 carrots (about 1/4 pound), coarsely chopped 

2 parsnips (about 1 pound), coarsely chopped 

1 celery stalk, coarsely chopped 

1 bunch red or green Swiss chard (about 1 1/2 pounds) 

Several sprigs fresh thyme 

Several sprigs parsley 

1 bay leaf 

Preparation

Melt butter and olive oil in a medium stockpot over medium-high heat. Add onions and cook, stirring, until onions are brown and caramelized, about 8 minutes. Add carrots, parsnips, and celery; cook until tender, about 15 minutes.

Wash and drain Swiss chard thoroughly. Chop into 1-inch pieces.

To cooked vegetable mixture, add Swiss chard, 14 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 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.