Equipment: One 9×13 inch-baking dish

1. Cook the macaroni: In a large pot, bring 4 quarts water to a rolling boil over medium heat. Add the salt and bring the water back to a boil. Taste the water. It should be salty like sea water. If it a little faint in salt taste, add additional salt. Add the macaroni and stir, with a wooden spoon or large slotted spoon, to ensure the macaroni does not stick to the bottom of the pot as it cooks. Cook until the macaroni is still quite firm, 6-8 minutes. Pour the macaroni and water into a strainer placed over the sink. Allow the water to drain out, reserving approximately 1 cup of the liquid.
2. Preheat the oven to 350F.
3. Make the sauce: In the same pot, bring the cream and the reserved cooking liquid to a simmer. Whisk in the mustard, Stir in 3 cups of the Gruyère. Season with salt and pepper to taste. Simmer gently; stirring constantly, until the cheese is melted and integrates with the cream. Add all but ½ cup of the Parmesan and all of the cheddar. Stir with a wooden spoon and simmer again until smooth. Add a splash of Worcestershire, Tabasco and the garlic. Stir to blend. Taste for seasoning.
4. Finish: Add the macaroni to the cream and stir gently to blend. Allow the macaroni to “rest” on the stove, 5-10 minutes, so the pasta absorbs the flavors. If needed, add the remaining ½ cup Gruyère. In a medium bowl, mix the butter and breadcrumbs. Season with salt and the remaining ½ cup Parmesan. Transfer the macaroni to an ovenproof baking dish and top with the breadcrumb mix. Place the dish in the center of the oven and bake 10-15 minutes or until hot and bubbling.