Preheat the oven to 350°F.1. In a pot of boiling salted water, blanch the cauliflower bouquets for 8 minutes. Drain. Reserve.2. Prepare the Mornay sauce as follows: make a roux with the butter and flour.3. Off the heat, add the lukewarm milk, salt, and pepper, while constantly stirring. The sauce will thicken slowly.4. Add the grated cheese and nutmeg. Season.5. Continue stirring until the cheese has completely melted.6. Butter the sides and bottom of a baking dish, then place the cauliflower bouquets in it. Season and cover with cheese sauce.7. Bake for 15-20 minutes and place under the broiler or grill to brown.