3/4 pound young green beans or 1 - 10 oz package frozen cut beans
6 tablespoons butter
1 medium onion, finely chopped
1 clove garlic, minced
1/2 cup finely chopped celery
8 cups chicken broth
1/3 cup pearl barley
1/2 teaspoon tarragon
6 to 8 sliced mushrooms or 1 - 4 oz can, drained
2 tablespoons butter
2 tablespoons flour
1/2 cup sour cream
1/4 cup chopped fresh parsley

If using fresh beans, trim the ends and line up on a cutting board a handful at a time. Chop until beans are the size of peas. If frozen, thaw and chop as above.

In medium saucepan heat 6 tablespoons butter until it foams, and add onion, garlic and celery. Cover and cook for 8 minutes.

Add the chopped beans and continue to cook, covered, for an additional 10 minutes over medium-low heat.

Pour the chicken stock into the saucepan with the vegetables. Add the barley and tarragon.  Bring to a gentle boil, reduce heat to a simmer and cook for 30 minutes.

Meanwhile sauté the mushrooms in 2 tablespoons of butter over medium heat for 10 minutes. Set aside.

When the soup has cooked for 30 minutes, transfer the mushrooms to the saucepan. Simmer for 15 more minutes and then remove from heat.

Whisk together the flour and sour cream. Beat 1 cup of the hot soup gradually into the sour cream. While stirring, slowly pour the sour cream mixture back into the saucepan.