I've eaten them raw, served sashimi style with wasabi and soy. Fantastic. They're also very good steamed. Better than boiled for me. They cook very quickly, like scallops.
Yep, sounds like you killed them with too cold a fridgeI bought them yesterday from an extremely reputable fishmonger - they were closed with just the foot hanging out. Overnight in a very cold fridge they have opened right out.