There are a number of ways of cooking a cauliflower but, as with asparagus, you are dealing with a vegetable which has two edible elements where one needs less cooking than the other. This is always problematic.
If you want to cook a cauliflower whole, start by stripping away the outer leaves, then cut out the centre of the stem at the base and place the cauliflower in a saucepan into which it will just fit in about 3.5 cm / 1.5 inches of rapidly boiling salted water and cover with a lid. The tougher stem area is now covered by boiling water, while the more tender florets will steam gently. It is impossible to give a precise cooking time because cauliflowers come in different sizes, but about 7โ8 minutes should suffice. You want to cook it to the point when the stem just gives to the tip of a knife or skewer.