rocketor watercress, lightly dressed, to serve (optional)
Heat oven to 220C/200C fan/gas 7. Remove the leaves from the cauliflower and cut out the base (without cutting away so much that the head collapses). Cut the cauliflower in half, then into four slices – two from each half – that are about 2cm thick. Put these on a baking sheet, brush all over with oil and season with pepper (no salt). Cover the baking sheet tightly with foil and cook for 12 mins.
Remove from the oven, take off the foil and turn the heat down to 200C/180C fan/gas 6. Put the sheet back and cook for 8 mins. Remove from the oven – the pieces should be golden on one side – and turn the cauliflower over. Put some of the taleggio, a slice of prosciutto and a spoonful of crème fraîche on each cauliflower piece. Sprinkle with the gruyère, then return to the oven.
Cook for another 8 mins, or until the cauliflower is golden and the cheese has melted. The cauliflower pieces should be completely tender. Serve straight away with the rocket or watercress, if you like.