Ingredients
6 tbsp. unsalted butter
Coarse salt and ground pepper
1 lb. medium pasta shells
1/4 c. all-purpose flour
1 tsp. dry mustard powder
4 c. whole milk
4 oz. sharp white Cheddar cheese
4 oz. Havarti cheese
4 oz. Muenster cheese
1 tsp. Worcestershire sauce
6 slice white sandwich bread
Preparation
Step 1Preheat oven to 400 degrees. Bring a large pot of water to a boil. Butter a shallow 4-quart baking dish (oval or 9-by-13-inch rectangle); set aside.Step 2Generously salt boiling water; add pasta. Cook, according to package instructions, until 2 minutes short of al dente. Drain pasta, and return to pot.Step 3While pasta is cooking, melt butter in a large saucepan over medium. Transfer 2 tablespoons melted butter to a small bowl; set aside for topping. Add flour and mustard powder to remaining butter in saucepan. Cook, whisking, 1 minute (do not let flour darken). Whisk in milk. Bring to a boil; reduce heat to medium-low, and simmer until sauce is thickened, 2 to 3 minutes.Step 4Remove sauce from heat. Gradually whisk in cheeses; add Worcestershire sauce, and season generously with salt and pepper. Add sauce to pasta, and toss to combine; transfer to prepared baking dish.Step 5Place bread in food processor; pulse until very coarse crumbs form (you should have about 3 cups). Add reserved melted butter, and pulse just to moisten. Scatter crumbs over pasta in baking dish. (If making ahead, cover and refrigerate up to 1 day.)Step 6Place dish on a rimmed baking sheet, and bake until topping is golden and sauce is bubbling, 15 to 20 minutes. (If refrigerated, bake for 30 to 35 minutes.) Cool 5 minutes before serving.
