Remove the leaves from the cauliflower, rinse it well and then cut out the core. Cut the remainder into four equal pieces
Bring a large pot of salted water to a boil and then add the cauliflower. Cook for 5-6 minutes, or until tender. Drain and put it into an ovenproof casserole dish.
Meanwhile, melt the butter in a saucepan over low heat.
Add the flour and stir with a wooden spoon to make a smooth paste.
Cook the mixture gently for a minute, then remove the pan from the heat.
Stir in the milk slowly
Return the pan to the heat and cook on low for 5-10 minutes, stirring frequently
Stir 3/4 of the cheese into the saucepan to melt
Season with the salt, pepper and nutmeg
When the sauce is melted, pour it over the cauliflower and sprinkle the reserved cheese and the bacon crumbles on top
Place under the broiler for a few minutes and until the top starts to bubble and brown