Heat the oven to 375°F. Bring the water to a boil in a large pot, then add the kosher salt.

Cook the cavatappi for 1 minute less than the package directions, until the centers still have a little firmness. Drain thoroughly without rinsing.

While the pasta cooks, melt 5 tablespoons butter in a saucepan over medium heat. Whisk in the flour and cook for 1 minute, then gradually whisk in the warmed whole milk and evaporated milk.

Simmer for 5 to 7 minutes, whisking often, until the sauce coats a spoon but still pours easily. Remove from the heat and stir in the Dijon mustard, garlic powder, onion powder, smoked paprika, and black pepper.

Set aside 1 1/2 cups of the combined shredded cheeses. Add the remaining cheese to the warm sauce by handfuls, stirring until smooth before adding more.

Fold the drained cavatappi into the cheese sauce until every curve is coated.

Transfer the pasta to the baking dish. Melt the remaining 2 tablespoons butter, toss it with the panko, and scatter the crumbs and reserved cheese evenly over the top.

Bake for 25 to 30 minutes, until the edges are bubbling and the top has deep golden patches. Rest for 5 to 10 minutes before serving so the sauce can settle.