Mushroom, Onion, and Barley Soup

Very tasty soup that is also very healthy! Makes about 10 cups of soup.

Ingredients:
1 teaspoon olive oil
1 onion sliced very thin
1 cup barley (I used quick cooking because that's what I had on hand)
2 teaspoons minced garlic
1 teaspoon dried thyme leaves
1/2 t dried marjoram
16 ounces sliced mushrooms (I used 8 oz. of regular mushrooms and 8 oz. of baby portabellas)
8 cups of fat free reduced sodium beef stock
1 tablespoon sherry
1 teaspoon Balsamic Vinegar
1 teaspoon salt
1/2 teaspoon black pepper
1 T cornstarch
1/4 cold water

Directions:
Heat the oil in a stock pot over medium heat. Add the onions, and sauté for about 5 minutes, or until they start to caramelize. Add the garlic, thyme, marjoram and mushrooms. Sauté for another 3 to 5 minutes.  Add in the sherry and vinegar, and stir to combine. Pour in the broth, add the barley, and bring to a boil. Reduce heat to low and add the salt and pepper. Cover the pot and allow the soup to simmer for an hour.  Whisk together the cornstarch and water and add to the soup to slightly thicken the broth.