Preheat oven to 400F. In a big saucepan, boil lightly salted water.
Return the macaroni-filled water to a boil. Cover and boil pasta for 8 minutes, tossing periodically, until firm. Drain after cooking.
Melt 1/4 cup butter in a large pot. When the butter foams and bubbles, stir in the flour and simmer for 3 to 4 minutes on medium heat.
Stir in 1 cup of milk after adding thyme, cayenne pepper, and white pepper. Rewhisk leftover milk. Simmer the sauce.
Worcestershire sauce, salt, and nutmeg. Cook on medium-low for 8 minutes, whisking regularly. Then add 2 1/4 cups Cheddar cheese. Add mustard.
Macaroni in casserole dish. Pour cheese sauce over pasta and mix.
Mix panko bread crumbs and 1 tablespoon melted butter and sprinkle over mac and cheese. 3/4 cup cheddar cheese goes on top.
Bake for 20 minutes until the bread crumbs and cheese are golden. Enjoy!