Bottarga is the salted roe of cod or tuna. I use bottarga di muggine, from cod, because it has a milder flavor than the tuna, bottarga di tonno. It’s sold by the piece and, kept tightly wrapped in the refrigerator, will last for months. It’s salty and has a pleasant fishy taste, not unlike anchovies. In Italy, it’s grated over pasta and is wonderful that way. It would also work perfectly as a garnish for risotto, or grated over salad.