Ika (squid) for sashimi - to blanch or not to blanch?
This is quite an old thread but I shall offer my two cents worth anyway.
Yes! you should blanch the squid but only for about 30 seconds. After skinning and gutting the squid I separate the legs, split the remaining tube longways and plunge into boiling water for 30 seconds. Immediately drain and plunge into cold water. After cool cut into serving size pieces which can be dipped into a wasabi and shoyu dipping sauce and enjoyed with steamed rice, miso soup, and some Japanese pickled veggies. Beer or sake are great beverages with which to enjoy this simple meal.
Almost always blanch. I've had the very thick skinned mongo-ika, a pacific "giant" squid, raw - but it was firm and thick. I think that most of the squid we get (Atlantic, Meditteranean) is just too thin and formless. You can score the meat to keep it from curling.
I used to do my own octopus and squid, but it's too much work. I buy the sashimi or nigiri sushi ready pieces cooked and frozen at the Japanese or Korean food stores. Since it's already cooked, it doesn't loose a lot in the freezing process, and I don't have to worry about overcooking (which really makes both of these meats very chewy). I'll buy an octopus once in a while so I can make sudako - then, I'll freeze each of the remaining tentacles whole to be thawed and sliced later. But otherwise, it's the pre-boiled, pre-cut, frozen stuff.