There's an invisible secret hidden in the wonderful soups of Italy: at their heart is always a truly great stock, or 'brood'. With this rich base, all you need to do is choose your extras. Will it be baked mountain cheese, or frittata slices? Ricotta dumplings or mussels, waiting to be pulled out of steaming black shells? Hearty mushrooms and pearl barley, or chickpea and pancetta? The choice is yours.