Cauliflower Cheese Soup

• 1 large cauliflower, weighing about 750 g (1 lb 10 oz)

Trim the outer green leaves off the cauliflower and cut it into florets. Heat the butter in a heavy-based saucepan, add the onion and leek, then cover and cook gently for 2-3 minutes, until the vegetables begin to soften. Do not let them brown. Add the cauliflower florets (reserving a few small ones as a garnish) and cook gently for 4-5 minutes. Pour in the stock or water, bring to the boil, th