In a large pot, bring the water to a rolling boil. Add the salt and bring the water back to a boil. Taste the water. It should be salty like sea water. If it's 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, 8-10 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.
In the same pot, bring the cream and the reserved cooking liquid to a simmer. Add the Dijon mustard and ¾ cups of the Gruyère. Season with salt and pepper to taste. Simmer gently; stirring constantly, until the cheese is melted and has integrated with the cream. Add the Parmesan and Cheddar. Stir with a wooden spoon and simmer again until smooth. Add a splash of Worcestershire and a splash of Tabasco. Stir to blend. Taste for seasoning.
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 Gruyère. Transfer the macaroni to an ovenproof baking dish (about 9 by 13 inches) and top with the breadcrumbs. Bake in the oven for 15 minutes before removing and serving a plate.