Gianduja is the Piedmontese marriage of chocolate and hazelnut — a smooth paste or firm bar made from roasted hazelnuts ground with sugar and cocoa into a silky, mahogany-brown mass in which the nut, not the cocoa, leads. Traditionally around 30 percent hazelnut, it is softer, sweeter and more meltingly rich than plain chocolate, and it is the direct ancestor of every chocolate-hazelnut spread that followed, Nutella included.