Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.

Bring a large pot of lightly salted water to a boil. Cook cavatappi in the boiling water, stirring occasionally, until tender yet firm to the bite, about 8 minutes. Drain.

While the pasta is cooking, melt butter in a large pot over medium-low heat. Whisk flour into melted butter until mixture has a thick, paste-like consistency, about 30 seconds. Slowly whisk in 2 cups milk until smooth. Stir in remaining milk, increase the heat to medium-high, and cook, whisking constantly, until thick and almost boiling, 5 to 10 minutes.

Add Gouda, Cheddar, Swiss, and 1 cup Parmesan; stir until cheeses melt and sauce is smooth. Fold in cooked cavatappi until coated. Pour mixture into the prepared baking dish.

Stir remaining 1/2 cup Parmesan cheese and bread crumbs together in a small bowl; sprinkle over cavatappi mixture, then drizzle truffle oil over top.

Bake in the preheated oven until sauce is bubbling and topping is golden, about 30 minutes. Cool for 10 minutes before serving.