They taste the best just before the tiny buds open but loose flavour very quickly afterwards. Remember that broccoli stalks are also great tasting and a terrific addition to Asian stir fries. When you pick the central head leave the plant in the ground. More often than not it will develop two smaller side heads which are equal in taste, if not volume, to the main one. Probably the next easiest to grow is cabbage, although cabbage tends to be a bit fussy with temperature.
Cauliflowers are a real surprise vegetable.
One day it looks like just a bunch of loose leaves, and then you look 3 or 4 days later and find a magnificent white head. Once the head forms take a few outer leaves, hold them together above the plant so that they cover the head, and tie off with a rubber band. Keeping the sun off the head will keep it white. Yellow heads still taste as good, but it's not quite the same. Cauliflowers need a lot of nitrogen, so plenty of well composted poo is in order.