2 lg. onions, minced
2 tbsp. butter
2 lbs. zucchini, scrubbed, trimmed, and sliced thin
4 c. chicken broth
1 1/2 tbsp. white wine vinegar
1 garlic cloves, minced
2 potatoes, peeled and sliced
Salt and pepper to taste

In a kettle saute onions in butter over moderate heat for 5 minutes. Add zucchini, broth, vinegar and garlic. Add salt and pepper. Bring to a boil, stirring occasionally, add potatoes, and simmer for 30 minutes covered. Let cool. In blender, puree soup in batches, transfer to bowl and chill covered for at least 2 hours. Ladle into chilled bowls and garnish with sour cream.