Preheat the oven to 350 degrees F.
Bring a large pot of salted water to a boil over high heat. Blanch
for 2 minutes. Transfer the cauliflower to a buttered 9 by 13-inch baking dish
and let cool, about 5 minutes.
In a small skillet over medium-high heat, brown the pancetta. Transfer to a small bowl and set aside.
In the same skillet, melt
the butter. Add the flour and stir until combined. Continue stirring for 2 minutes to cook the flour. Slowly add the milk, stirring continuously until the milk
has incorporated and there are no lumps. Add the garlic clove
and red pepper flakes
and stir the sauce
over low heat until the mixture coats the back of a wooden spoon. Add the Parmesan, salt, pepper, nutmeg, and the reserved pancetta
. Stir to combine. Pour the sauce over the cauliflower to cover. Top with a sprinkling of bread crumbs.
Bake until the breadcrumbs
are golden and the cauliflower is cooked, about 25 minutes. Serve immediately.