Heat the oil in a large heavy pot over medium heat. Add the onions, celery, bell peppers, salt, cayenne, black pepper, and bay leaves. Cook, stirring often, for about 5 minutes, or until the vegetables are wilted. Add the stock and beans, stirring to mix well. Reduce the heat to medium-low and simmer, uncovered, until the mixture is smooth and creamy, 1 1/2 to 2 hours.
Just before serving, add the sherry, green onions, parsley, and hot sauce. Remove the bay leaves.
Serve hot in soup bowls.