Italian Mushroom Soup
["1/2 c. (1 stick) butter", "1 lb. mushrooms, thinly sliced", "1 large onion, minced", "3 Tbsp. tomato paste", "5 c. rich beef stock", "1/2 c. sweet vermouth", "salt and freshly ground pepper", "freshly grated Parmesan cheese"]
["Melt butter in a heavy medium saucepan over medium-low heat. Add mushrooms and onion; cook until onion is translucent, stirring occasionally, about 10 minutes.", "Stir in tomato paste.", "Add stock and vermouth; simmer 10 minutes to blend flavors.", "Degrease soup, if necessary.", "Season with salt and pepper.", "Serve immediately, passing Parmesan cheese separately.", "Makes 4 to 6 servings."]
["butter", "mushrooms", "onion", "tomato paste", "rich beef", "sweet vermouth", "salt", "Parmesan cheese"]