Soak the clams in water for half an hour, to ensure they are fully purged of all sand and grit.
Heat a toban over a very high heat and add the clams directly to it. They will bounce and sizzle as they begin to release their juices. Reduce the heat, cover with a lid and cook for a further 2 minutes. Once all the clams have opened, add the butter, sake, soy sauce, lemon juice, ichimi chil