Wash cauliflower well just before using. Cut it into florets by pulling away the leaves and cutting around the core on the underside. Separate the florets by cutting them apart from the inside of the cauliflower. The green leaves at the base are edible, but have a stronger flavor than the florets. Adding a tablespoon of lemon juice or a cup of milk to the cooking water will prevent discoloration. Cut cauliflower into large florets, toss with olive oil and fresh thyme, and roast, or steam it and serve with a light cream or cheese sauce.