1 (3-pound) head of cauliflower, cut into large florets
Kosher salt
4 tablespoons (1/2 stick) unsalted butter, divided
3 tablespoons all-purpose flour
2 cups hot milk
1/2 teaspoon freshly ground black pepper
1/4 teaspoon grated nutmeg
3/4 cup grated Gruyère cheese, divided
1/2 cup grated Parmesan cheese
1/4 cup fresh bread crumbs

Preheat the oven to 375°F.

Cook the cauliflower florets in a large pot of boiling salted water for 5 to 6 minutes, until tender but still firm. Drain.

Melt 2 tablespoons of the butter in a medium saucepan over low heat. Add the flour, stirring constantly with a wooden spoon for 2 minutes. Pour the hot milk into the butter-flour mixture and stir until it comes to a boil. Boil for 1 minute, whisking constantly until thickened. Remove from the heat, then add 1 teaspoon of salt, the pepper, nutmeg, 1/2 cup of the Gruyère, and the Parmesan cheese.

Pour one third of the sauce on the bottom of an 8 x 11 x 2-inch baking dish. Place the drained cauliflower on top and then spread the rest of the sauce evenly on top. Combine the bread crumbs with the remaining 1/4 cup of Gruyère and sprinkle on top. Melt the remaining butter. Drizzle over the gratin. Sprinkle with salt and pepper. Bake for 25 to 30 minutes, until the top is browned. Serve hot or at room temperature.

 Adapted from the Barefoot Contessa