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1
Preheat oven to 375 degrees F (190 degrees C).
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2
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes; drain.
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3
Melt butter in a large pot over medium-low heat. Slowly add flour to butter, whisking constantly; cook until brown and the mixture no longer smells of flour, about 5 minutes. Pour 1 cup milk into the flour mixture, whisking continually until fully incorporated, about 45 seconds; repeat twice. Add remaining 3 cups milk to the mixture, whisking to incorporate. Stir Worcestershire sauce, mustard powder, onion powder, and cayenne pepper into the mixture; season with salt and black pepper.
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4
Reduce heat to low. Cook sauce, whisking frequently, until it begins to thicken, about 10 minutes. Add about half the package of shredded Cheddar cheese; stir continually until the cheese melts completely. Repeat with remaining half package of Cheddar cheese and the American cheese, about 4 ounces at a time. Once cheese is entirely incorporated, remove sauce from heat.
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5
Stir drained macaroni into the cheese sauce to coat. Divide macaroni between two 9x13-inch baking dishes.
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6
Mix crushed potato chips, 1 cup shredded Cheddar cheese, and Parmesan cheese in a bowl. Top the macaroni with the potato chip mixture evenly. Spray the potato chip mixture with cooking spray.
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7
Bake in preheated oven until the crust is golden brown and the sauce is bubbling, 35 to 45 minutes.
