Step 1

Preheat the oven to 350 degrees F. Butter a 9-by-13-inch baking dish.

Step 2

Bring a large pot of water to a boil and season with a generous amount of salt. Boil the pasta until al dente, 2 to 3 minutes less than the package instructions.

Step 3

Meanwhile, in a large pot over medium heat, add the evaporated milk and Dijon and whisk together. Bring to a simmer. Toss the Cheddar, shelf-stable cheese and cornstarch together in a bowl until totally coated. Stir into the sauce cheese and heat, stirring constantly, until the cheese is melted and the sauce is silky and smooth, about 5 minutes.

Step 4

Drain the pasta, then add to the cheese sauce and stir to coat. Transfer to the prepared baking dish.

Step 5

Sprinkle an even layer of the mozzarella over the top. Drizzle the barbecue sauce over the cheese, and top with a thick layer of crumbled potato chips.

Step 6

Bake, uncovered, until gooey and bubbling, 30 to 35 minutes. Serve hot.