it's a dried fish roe made from tuna or mullet that is sold that can be shaved/grated/sliced over salads, pasta, eggs, etc. it's great stuff.
i'm thinking a crisp white as well ... i've got a bottle of naia in that will work if i can't think of anything else.
Bottarga is grey mullet roe - dried/pressed - a speciality from Sardinia - and Sicily maybe? I think it is also found in southern France - "bottargue". Absolutely a delicious delicacy - wonderful shave on pasta.
I'm not sure if I know how to insert links, but here goes:
This is from the San Francisco Chronicle -
Bottarga captures Bay Area's fancy
And here's a place that sells it -
Bottarga is one of my favorite food items. There are many fish whose roe can be dried and pressed into bottarga. MMRuth mentions mullet, but I had bottarga di tono earlier this year on some gnocchi in an Albacore dish......stellar. It can be tricky to locate and purchase; a good place to start would be an authentic Italian market, possibly having them bring it in for you. Hopefully there is one in your city, give it a try! If you see it on a restaurant menu, go for it, or ask the server to ask the chef where he gets his and piggyback a small order through him.