Cut the cauliflowers into florets and chop the remaining stalk into 0.5cm dice. Peel and finely chop the onion and garlic.
Melt the butter in a large pan, add the onion, garlic and thyme sprigs and cook over a low heat until softened but not coloured.
Add the cauliflower florets and stock, bring to the boil, reduce the heat and simmer for 15-20 minutes until the florets are tender.
Remove from the heat and leave to cool.
Bring a small pan of salted water to the boil, add the chopped cauliflower stalk and cook for a minute or two until tender. Drain and refresh with cold water. Drain again and set aside.
Coarsely grate the gruyère and chop the parsley.
Pick out the thyme and blend the soup in batches until very smooth.
Season well and pour back into the pan. Reheat with the cream or mile, adding the blanched cauliflower stalk and parsley at the end and check the seasoning.
Ladle the soup into bowls, stir a spoonful of tapenade into each and scatter with a little grated gruyère.
((Annie Nichols in The Sunday Telegraph-Stella))
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