Purple sprouting broccoli gratin

Method

1. Halve the stems of sprouting broccoli and peel the lower halves if thick and tough. Put the milk, onion, bay leaves, mace and peppercorns into a small pan, bring slowly to the boil, then set aside off the heat for at least 20 minutes to allow the flavours to infuse.
2. Bring the infused milk back to the boil, then strain it into a jug (discard the flavourings). Melt the butter in a medium pan, stir in the flour and cook gently for 1 minute. Remove from the heat and gradually beat in the hot milk. Return to the boil, stirring, then simmer for 5 minutes, stirring now and then. Stir in the cream, nutmeg and some salt and white pepper to taste. Keep warm over a very low heat, continuing to stir the mixture now and then so a skin doesn’t form.
3. Preheat the grill to high. Put the broccoli in a steamer (or colander/sieve) set over a pan of boiling water, sprinkle with salt, cover and steam until just tender (freshly picked will take no more than 3 minutes, shop-bought may take 5-6 minutes). Drain the broccoli, wait for the steam to die down, then lay over the base of a large, lightly buttered, shallow ovenproof dish. Pour over the warm sauce, then sprinkle with the grated cheddar. Grill for 4-5 minutes or until the top is golden in places and bubbling.