Bottarga is dried, salted roe from either the Mediterranean tuna (tonno in Italian) or the gray mullet (mugine).
Bottarga di tonno (also known as uovo di tonno, or tuna eggs) and bottarga di mugine are local specialties of Sicily and Sardinia. Italy’s two large Mediterranean islands, and are valued as delicacies in the rest of Italy.
The roe sac is removed as soon as the female fish is caught. It is then washed; salted; pressed, traditionally between wooden plank s or marble slabs; and dried, traditionally in the sun, for one or two months.
It comes out looking like dark amber wooden boards, firm enough to be grated like Parmesan cheese. The salt helps the drying process by extracting water from the crushed eggs, which glue themselves together because of their albumen and fat.
Tuna bottarga has a bright, sharp salty flavor, whereas the mullet version is somewhat milder. The best thing to do with either is the simplest: make Sardinia’s spaghetti alla bottarga. To a plate of cooked spaghetti, add extra-virgin olive oil, chopped garlic, parsley, and red pepper flakes. Toss, and grate some bottarga over the top before serving.
Remember that bottarga is a condiment, quite salty and fishy , and a little goes a long way.