In a large saucepan, heat olive oil or cooking oil. Add all of the mushrooms and garlic. Cook, stirring occasionally, about 10 minutes or until mushrooms have softened and most of the liquid has evaporated. Stir in sherry, if desired. Cook for 2 minutes more.
Add the chicken broth and dried thyme (if using). Bring to boiling; reduce heat. Simmer, covered, for 20 minutes. Stir in the snipped fresh thyme (if using). Ladle into soup bowls. Makes 6 servings.