The Periwinkle is a species of small edible sea snail. Periwinkle is a gas- tropods that show up in so many of the great cuisines of the world, the bistro favorite of snails broiled in garlic butter; Asians stir-fry in their sea or river water juiciness; and in most coastal areas around the world, it's common to simply boil periwinkles in seawater and eat them as well.