Bread crumb topping: heat the oven to 350°F. Mix the bread crumbs and melted butter in a small baking pan and bake until golden brown and crisp, 15 to 20 minutes; set aside.

Mix the eggs, 1 cup of the evaporated milk, hot sauce, 1/2 teaspoon salt, pepper, and the mustard mixture in a small bowl; set aside.

Bring 2 quarts water to a boil in a large heavy saucepan or Dutch oven. Add the remaining 1 1/2 teaspoons salt and the macaroni; cook until almost tender but still firm to the bite. Drain and return to the pan over low heat. Add the butter and toss to melt.

Pour the egg mixture over the buttered noodles along with three-quarters of the cheese; stir until combined and the cheese starts to melt. Gradually add the remaining milk and cheese, stirring constantly, until the mixture is hot and creamy, about 5 minutes. Serve immediately, topped with the toasted bread crumbs.