Preheat the oven to 350 F. Grease a 9-by-13-inch baking pan with butter.
Place a large saucepan of water over medium heat, add the salt, and bring it to a boil. Add the macaroni and cook for 2 to 3 minutes less than indicated on the package. Don't overcook and don't rinse. Drain the macaroni well in a colander, return it to the pot, and add the olive oil. Gently stir to coat so the macaroni doesn't stick together.
Set aside ¼ cup of the shredded cheddar and ¼ cup of the shredded Monterey Jack for topping.
In a large bowl, use a wooden spoon to combine the eggs, milk, sour cream, butter and mustard powder. Add the Velveeta, remaining cheddar and remaining Monterey Jack, stirring well. Add the macaroni to the mixture and stir until well combined and the macaroni is nicely coated.
Transfer the mixture to the prepared pan, spreading it evenly, and sprinkle the top with the reserved cheddar and Monterey Jack cheeses. Bake until the cheeses are bubbly, 20 to 25 minutes.
Remove from the oven and let rest for 15 to 20 minutes to thicken before serving.
Source: u/Pleasant-Medicine-43
Link:
https://www.reddit.com/r/macandcheese/s/KJCm5QmlsS