5 tablespoons unsalted butter, divided3 tablespoons unbleached all-purpose flour2½ cups whole or low fat milkCoarse salt¼ teaspoon dry mustard, optionalPinch freshly grated nutmeg, optionalPinch fresh black pepper3 cups grated extra-sharp cheddar, divided½ cup grated Parmesan, divided1 pound elbow macaroni cup coarse fresh breadcrumbsPreheat the oven to 375 degrees. Melt 3 tablespoons butter in a medium, heavy-based saucepan over medium heat. Add flour and whisk until smooth. Cook 2-3 minutes, whisking frequently. Slowly add milk, whisking vigorously. Lower heat and simmer 7-8 minutes, whisking frequently, until creamy and smooth. Add 1½ teaspoons salt, the mustard, nutmeg and black pepper.Remove from heat and add 2½

cups cheddar and ¼

cup Parmesan. Whisk until cheese melts and the sauce is smooth. Taste and adjust seasonings. It should be salted well, as the sauce flavors the macaroni.Meanwhile, bring a large pot of water to a boil, add 2 tablespoons salt, and boil the macaroni according to the package directions. Drain well, return to the pot, then toss with the sauce until thoroughly coated. Pile into a 13- by 9-inch baking dish or four 6-inch cast-iron skillets. Sprinkle evenly with the remaining cheeses.Melt the remaining 2 tablespoons butter and toss with breadcrumbs; distribute over the macaroni. Bake until topping is browned and the macaroni hot, about 20 minutes. Let rest for about 10 minutes before serving.Variations: For a smoky green chile version, add 1 drained 4-ounce can diced mild green chiles before you put the macaroni in the baking dish. Mix 1 teaspoon smoked paprika with the crumbs and butter.For the “tuna melt” version, substitute 1 cup grated Havarti or Fontina cheese for 1 cup of the cheddar when you make the sauce (you’ll still need a total of 3 cups cheese plus the ½ cup Parmesan). Add two drained 5-ounce cans tuna and 2 teaspoons grated lemon zest to the macaroni before you put it in the baking dish.

From “Simple Comforts: 50 Heartwarming Recipes” (Sur La Table/Andrews McMeel Publishing, 136 pp, $15).