I learned of this savory seasoning (spelled differently in each region) last year on the great show 'Bizarre Foods with Andrew Zimmern' shot on coastal Italy. It is VERY expensive but I made mine for next to free. It is raw fish roe sacks fermented and dried for months packed in salt. It is shaved onto hot pasta and other dishes where it lends a flavor like anchovy but less sharp and not all all oily....more like a very dry Parmesan. Last Thanksgiving my friend Pat's fishing buddy Paul gave me two BIG pregnant mullets he'd just caught as he and his wife don't like mullet. I removed the roe sacks, cooked and ate the mullets, then did the following.
I hope to strike an arrangement with a commercial mullet fisherman as they discard the roe, and make botargo in bulk in a large wooden box packed with salt like I saw on Andrew's show that night. Yummy!