Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch glass baking dish.
Fill a large pot with lightly salted water and bring to a rolling boil over high heat. Once water is boiling, stir in macaroni and return to a boil. Cook pasta uncovered, stirring occasionally, until pasta has cooked through, but is still firm to the bite, about 8 minutes. Drain and mix with 1/2 of the butter.
While macaroni is boiling, melt remaining butter in a saucepan over medium heat. Stir in onions, and cook until they begin to soften, about 3 minutes. Stir in flour, and cook 5 minutes longer. Add milk and bring to a simmer, stirring frequently. Cook and stir until milk has thickened, about 10 minutes.
Once thick and smooth, stir in salt, white pepper, Worcestershire sauce, hot pepper sauce, mustard, 2 cups Cheddar cheese, and 1/4 cup Parmesan cheese. Stir until cheeses have melted, then stir in macaroni until evenly coated. Scrape into the prepared baking dish and smooth the top. Toss remaining 1 cup Cheddar cheese and 1/4 cup Parmesan cheese with bread crumbs in a mixing bowl. Sprinkle evenly over macaroni.
Bake in the preheated oven until macaroni is hot and crust is golden brown, about 30 minutes.
Nutritional Facts
Per 12 servings
Calories: 286
Carbohydrate: 23g
Fat: 16g
Fiber: 1g
Protein: 13g
Sugar: 3g
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