Fill a pot with six cups of water and set it to boil.
Shred medium cheddar cheese and Gruyère cheese.
Thinly slice green onions.
Add a hefty pinch of salt to boiling water, followed by dried macaroni. Cook for six minutes, stirring occasionally.
Reserve some pasta water, then strain cooked pasta.
In the pot on low heat, add unsalted butter, whole milk, grated cheeses, and cheese packet. Decide on cream cheese or sour cream for thickness.
Stir until cheese is melted and emulsified, adding reserved pasta water as needed.
Fold in cooked macaroni and garnish with green onions.
For Cheese Burger Mac & Cheese, prepare ground beef, bacon, and onion mixture, season, and cook.
For Pizza Mac & Cheese, prepare sauce with butter, sun-dried tomatoes, tomato paste, garlic powder, and oregano, then add milk and cheeses.
Top with mozzarella and pepperoni, broil until melted, and finish with basil and Parmigiano-Reggiano.
