sea urchin, urchin roe.
Uni (pronounced OO-nee, "OO" as in food) is the Japanese name for sea urchin and refers to the bright orange reproductive organs contained inside the spiny shell. The pieces vary in size from under an inch to 3" long and the color can vary from pale yellow to dark golden orange.
What's it taste like?
They have a creamy texture that melts in your mouth with a sweet briny flavour that can be slightly nutty. When eaten raw, it is slightly slimy making it an acquired taste for many, but when cooked it firms up giving it a texture similar to cheese.
Where do I get it?
Uni is typically packaged in small flats and sold in Japanese grocery stores. In recent years it's started to show up at fish mongers whole, but you will have to shell and clean them yourself.
When is it best?
Uni is available all year long, but look for firm pieces that are roughly uniform in color. Their surface should have a slightly rough appearance and they should not be visibly slimy or smooth, which would indicate they were either over handled or sat in water too long during processing.
How do I use it?
The most common way to eat it is raw, either as sashimi or in sushi. They are also good steamed in sake, or mixed into sauces or pastas.