5ml(1 tsp.) sea salt, plus more for salting pasta water
20ml(4 tsp.) white mustard powder
60grams(1 cup) your favorite potato chips, fried in high quality fat like olive oil, lard, tallow, avocado oil or coconut oil
Optional
60grams(1/4 cup) salami, cooked bacon, grass fed beef hot dogs, pancetta or other cured meats, diced into 1/4" pieces
Instructions
Make Macaroni
Pour dry pasta in a heavy saucepot. Add just enough water to completely cover the pasta and add a heavy pinch of sea salt.
Bring to a boil over medium-high heat, cooking pasta to al dente (1-2 minutes less than you'd normally cook it), about 15 minutes total. Drain and set aside.
Shred the cheeses coarsely.
Preheat oven to 400F. Grease a baking pan (8 or 9 inch square) with butter and set aside.
Make a Roux
Melt butter over low-medium heat in the saucepot.
Add flour slowly, incorporating into the butter with a whisk. Continue stirring until it becomes aromatic and turns golden brown, about 5 minutes.
Make Béchamel sauce
Stir in the milk and heavy cream and raise heat to medium high.
Whisk constantly to prevent dairy from burning on bottom of pot.
Lower heat to a simmer. When sauce coats the back of a spoon, it's the right thickness.
Add salt, pepper and mustard powder and whisk.
Make Cheese sauce
Add shredded cheeses in 3 batches, ensuring that each batch is completely melted into the pot before adding the next.
Remove from heat and mix pasta into pot well.
If using, stir diced meat into pot.
Bake
Pour mixture into buttered baking dish.
Crumble potato chips to coat top of casserole.
Bake 20-22 minutes. You may wish to set broiler on low for the last 3 minutes. if you do, keep an eye on it; the crust can burn easily.