Directions

1. Place a pasta pot on the stove, add water and a good amount of kosher salt and bring to a boil. Follow cooking instructions on the package. I try to time my pasta to when my sauce finishes and typically drop it in the boiling water once I have added the slurry. The sauce simmers while the pasta cooks and they are done at about the same time.
2. In a large non-reactive sauce pot over medium heat add the whole milk, heavy cream, and garlic and bring to a gentle simmer.
3. Add cream cheese and whisk thoroughly to break up and melt out. Once melted, add the American cheese slices whisking occasionally to completely melt.
4. In 2 additions add cheddar to the pot mixing well in-between. Once fully melted and no strings remain on your whisk, add the gruyere and let melt completely. Finally, add the parm whisking constantly. Whisk in the sriracha (if using), and the mustard powder.
5. In a small bowl combine the cornstarch and water to make a slurry. Make sure the sauce returns to a gentle simmer and add the slurry, whisking well. Turn down the heat and let cook for 10 remaining minutes for the cornstarch to fully thicken. If you like your mac on the thick-side feel free to add additional slurry to taste.