I just bought one sea urchin at one of the seafood wholesalers in LA. Heavier the better.
I just cut around the mouth, dumped out the innards, split the shell in half, then rinsed the inside very carefully with cold water, then used a spoon to remove the roe from the shell, and placed the roe into salted water (I was using about a teaspoon per pint; you can add a touch of lemon juice if you'd like, but I prefer just salt water).
I let the roe soak in salted water (which helps remove the black membrane it's attached to), then rinsed and repeated this very carefully until the black membrane and other parts rinsed off. I then drained the roe on paper towels, chilled them and had lunch.
I got about 8 really nice sized pieces out of one urchin.
Where I live you can dive off the point and collect sea urchin. The catch limit is 10 per person, we also have black lip abalone, but there is a bag limit of 2 on those. Still nothing better than free seafood
I'm one of them But there's something about any kind of roe that doesn't work for me, I just get severly sick from it - and I kept trying them.... But even a few little tobiko morsels on a piece of sushi are enough. Seems like a strange and very specific reaction and I have never figured out where that comes from. Doesn't seem to be an allergy, though.