- Cook the cauliflower in boiling salted water for 10-15 minutes until tender. Drain and place in a flameproof dish.
- Meanwhile, place the milk, flour and butter in a saucepan. Heat, stirring continuously until the sauce thickens, boils and is smooth. Cook for a further 2 minutes.
- Add about three-quarters of the grated cheese to the sauce. Season with salt and pepper to taste.
- Add the mustard and nutmeg. Stir and cook for another minute.
- Pour the sauce over the cauliflower. Mix the remaining cheese and breadcrumbs together, sprinkle over the sauce. Grill until golden.
- Serve immediately.