Ruth Reichl's Mac & Cheese

Ruth Reichl’s Mac & Cheese
(simply the best mac & cheese ever!)

Ingredients:
FOR TOPPING
• ¼ stick (two tablespoons) unsalted butter, melted
• 2 cups panko (Japanese bread crumbs)
• 1 cup coarsely grated extra-sharp Cheddar (about 4 ounces)
Sauce:
• 3 tablespoons unsalted butter
• 3 tablespoons all-purpose flour
• ½ teaspoon red pepper flakes
• 2 ¾ cups whole milk
• ¾ cups heavy cream
• 4 cups coarsely grated extra-sharp Cheddar (about 1 pound)
• 2 teaspoons Dijon mustard
• 1 ½ teaspoons salt
• ¼ teaspoon freshly ground black pepper
• ¾ pound elbow macaroni
Put a rack in the middle of the oven and preheat oven to 400 degrees F. Butter a 3-quart shallow baking dish.
MAKE THE TOPPING: Stir together butter, panko, and cheese in a bowl until well combined.
MAKE THE SAUCE: Melt butter in a 5-quart heavy pot over moderately low heat. Whisk in flour and red pepper flakes and cook, whisking, for 3 minutes to make a roux. Whisk in milk in a slow stream, then bring sauce to a boil, whisking constantly. Simmer, whisking occasionally, for 3 minutes. Stir in cream, Cheddar, mustard, salt, and pepper. Remove pot from heat and cover surface of sauce with wax paper to prevent a skin from forming.
COOK THE MACARONI AND ASSEMBLE THE DISH: Cook macaroni in a 6-quart pot of boiling salted water (1 tablespoon salt per every 4 quarts of water) until al dente. Reserve 1 cup pasta cooking water and drain macaroni.
Stir together macaroni, reserved cooking water, and sauce in a large bowl, the transfer to baking dish (mixture will be loose).
Sprinkle topping evenly over macaroni. Bake until top is golden and bubbling, 25 to 35 minutes.