Remove core from cauliflower and place core-side down in a pan with about 1 C water. Cover pan and steam until tender but firm.
Melt butter in a sauce pan and blend flour over medium heat making a roux. Allow to cook for about two minutes.
Whisk in milk and cooking juices from cauliflower, and season with salt, pepper and a dash of nutmeg.
Transfer cauliflower to a baking dish, and cut out stems to separate florettes. Turn florettes stem side down, coarsely chop the stems which you earlier cut out, and spread them around the side of the baking dish.
Sprinkle cauliflower with about one third of the swiss cheese.
Add cream to sauce return to the boil and pour over cauliflower.
Sprinkle the gratin with remaining cheese and bake for 20 minutes in a 375º oven
Variation: Add 1-2 T dijon mustard to sauce before pouring over cauliflower.
