Cook the pasta per the manufacturer's al dente specifications, then rinse with cold water in a colander. Set aside. Preheat the oven to 375 degrees F.
In a 4-quart Dutch oven, melt the butter over low heat, then add the flour, stirring until thickened. Add the cream, evaporated milk, cayenne pepper and some salt and pepper, then whisk until thickened to the point that the sauce coats the back of a wooden spoon, about 5 minutes. Turn off the heat.
In a small bowl, whisk together the yolks and a tablespoon or two of the white sauce to temper the yolks, stirring constantly. Add the tempered yolks back to the white sauce, whisking, then add the Cheddar, followed by the American cheese, stirring until the cheese has melted completely. (If the cheese is not melting completely, return the saucepan to the stovetop over low heat and stir just until the cheese melts.) Gently stir in the pasta until coated. (The mac and cheese can be served at this point if desired, for a stovetop version.)
Turn the mixture out into a 9-by-13-inch baking dish. Crumble the chips on top of the mac and cheese and bake until golden brown and bubbling, 20 to 30 minutes. (If traveling with the mac and cheese, put a lid on it and bake on-site, preferably over a campfire!)