Sweet chestnuts, one of the most beloved Portuguese snacks, are key ingredients for the preparation of this traditional soup called sopa de castanhas. The soup is typically prepared with boiled or roasted chestnuts which have been peeled before being cooked in water or broth (either vegetable or chicken broth) along with ingredients such as onions, carrots, celery, garlic, olive oil, and butter.
There are numerous variations on the soup, and other common ingredients that may be used include red beans, potatoes, leeks, cabbage, or pieces of stale bread. This simple chestnut soup is usually flavored with parsley, cloves, bay leaves, salt, and pepper, and it can (sometimes) be enhanced with the addition of bacon or ham.