Trim the cauliflower an cut into florets. Bring a pan of lightly salted water to a boil. Drop in the cauliflower an cook 5 to 8 minor until just tender. Drain an transfer the florets into an ovenproof dish.
To make sauce, Melt the butter in a pan, stir in the flour cook gently, stirring constantly, for about 1 min do not let it brown. remove from heat an gradually stir in milk. Return the pan to the heat an cook, stirring, until the mixture thickens an comes to a boil. simmer gently for 1-2 mins.
stir in three-quarters of the cheese an season to taste with salt an pepper. spoon the sauce over the cauliflower an sprinkle the remaining cheese on top. put under the broiler in oven an broil to a golden brown. ummmmmmmm