Twice-Cooked Tuscan Bread Soup

This is one of Tuscany’s most famous culinary improvisations: An attempt to stretch classic minestrone soup by adding bread resulted in a brand-new classic. When freshly made, this is a hearty yet brothy soup; when reheated the next day, it thickens to a flavorful, porridge-like stew. Zolfini beans, a pale yellow heirloom variety, may be hard to find; cannellini beans make a fine substitute.