Boil the cauliflower in salted water for 5 minutes. Drain and arrange on the bottom of an overproof serving dish.

Put the milk, flour and butter in a pan. Bring to the boil while whisking continually. Simmer for 2 minutes with whisking.

Turn off the heat and whisk in about ¾ of the grated cheese.
Pour the cheese sauce over the cauliflower, season with ground black pepper, then sprinkle on the remaining cheese.

It will keep for several days in the fridge so there should never be any leftovers to throw away.