Macaroni and Cheese

Ingredients

• 6 tablespoons unsalted butter, plus more to grease the baking dish
• 1 cup panko bread crumbs
• 24 ounces sharp or extra-sharp Cheddar, grated (about 9 cups total)
• 1 pound elbow macaroni
• 3 1/4 cups whole milk
• 3 tablespoons all-purpose flour
• 1 1/2 teaspoons dry mustard
• 1 teaspoon fine sea salt
• 1/2 teaspoon freshly ground black pepper
• Equipment: 9- by 13-inch baking dish, flat-edged wooden spoon or heat-safe rubber spatula

Steps

1. Set the oven to preheat at 350°F and give a 9- by 13-inch baking dish a light coating of butter.
2. Melt 3 tablespoons butter over moderate heat in a small saucepan. Put the panko in a small bowl, drizzle the melted butter over it and toss. Toss in a handful of grated cheese, then set aside.
3. Cook the elbow macaroni al dente in a large pot of boiling salted water. Drain without rinsing and return the noodles to their cooking pot.
4. Warm the milk over moderate heat in a small saucepan only until it steams and tiny bubbles appear around the edges. Keep it from boiling, then take it off the heat.
5. In a medium saucepan over moderate heat, melt the remaining 3 tablespoons butter. Add flour and stir with a flat-edged wooden spoon or heat-safe rubber spatula, scraping the pan bottom to prevent burning, just until it starts to turn light brown, about 3 minutes. Add the warm milk slowly while stirring constantly until thickened, about 3 minutes. Remove from the heat, stir in dry mustard, salt and pepper, then stir in the remaining grated cheese until completely melted. Adjust seasoning to taste. Pour the cheese sauce over the cooked macaroni and stir gently to coat.
6. Pour into the prepared baking dish and add the panko-cheese topping. Bake to light golden brown and bubbling, about 30 minutes, and serve hot. To make ahead, put the macaroni and cheese in the baking dish, cool completely, cover and refrigerate for 2 days. Leave off the bread crumbs until ready to bake. Chilled macaroni and cheese may need longer than 30 minutes to cook fully.