Creamy gratins are a comforting backbone of winter cooking. Using cauliflower as the base gives you a healthy-ish dish, where the florets are enveloped in a rich, luscious béchamel sauce. I love adding diced ham or bacon, but you can easily omit it if you want a vegetarian option. It can be a whole dinner in itself, served with a salad, or a side dish as part of a buffet. I love the simplicity of this dish, and the groans of pleasure that I hear when I serve it to family and friends.   Serves 4 to 6 1 large head cauliflower (about 2 pounds), leaves removed, cut into florets 4 ounces bacon (about 4 strips), cut into 1/2 inch strips 3 tablespoons butter   1 tablespoon all-purpose flour   1 cup milk   1 cup half-and-half   1/4 teaspoon grated nutmeg   1/4 teaspoon sea salt  1/4 teaspoon freshly ground black pepper   1 cup grated …