1. Separate the flowerets from stalks of broccoli. Peel and split stalks lengthwise. In a large saucepan with plenty of boiling salted water add the broccoli stalks and cook until tender (do not let the water stop boiling). Add the flowerets and cook until tender. Drain under cold running water.
2. Make a purée with the broccoli in a blender or food processor. Season to taste and blend with melted butter. Stir cream or yogurt into the purée. Serve hot.