Unusually for a salad, this enjoys sitting, getting to know its dressing. It is inspired by Ellen Hooberman, a master of the caper, garlic and chopped parsley, which is a good thing!
Soak the butter beans overnight in cold water, then drain and cook in clean water with the heads of garlic (this can take 2–3 hours) so that you have your aforementioned pillows of joy.
Whisk all the dressing ingredients together thoroughly, adding salt and pepper to taste.
Take the cauliflower and butter beans and liberally dress them. Toss and then leave to sit overnight.
When it comes time to serve, just tease the leeks for a moment in some boiling salted water. The warmth of the leek, added to the cauliflower and butter beans, should awaken the slumbering salad. Once awake, it may need some more dressing—take a view. Add the chopped parsley and a substantial handful of capers. Toss vigorously, being careful not to crush the butter beans, then serve.