Preheat the grill to high. Cook the cauliflower in a pan of boiling salted water for 3 to 5 minutes, or until just tender. Drain.

While the cauliflower is cooking, melt 25 g (1 oz) of the butter in a frying pan. When bubbling add the pancetta and fry for 3 minutes. Reduce the heat and add the mushrooms, then cook for a further 2 minutes. Remove and drain on kitchen paper.

Melt the remaining butter in a pan. Add the flour, mustard and cayenne pepper to make a roux. Stir over a medium heat for 1 minute. Remove the pan from the heat and gradually stir in the milk.

Return the pan to the heat and stir until boiling, then reduce the heat and simmer for a further 2 minutes. Remove the pan from the heat and stir in 25 g (1 oz) of the cheddar and the parsley, then season to taste.

Mix together the cauliflower, pancetta and mushrooms and spoon into a shallow heatproof dish. Pour the sauce over and sprinkle with the remaining cheddar and breadcrumbs. Place under the grill until golden and bubbling. Serve straight away.