Spray a 9x13-inch baking dish with cooking spray. Set aside.

Using a cheese grater or food processor fitted with a grating attachment, grate the Cheddar cheese. Set aside.

Cut the cream cheese into 1/2-inch cubes. Set aside.

Place the elbow macaroni, milk, butter, and salt in a large pot. Cover the pot with a fitted lid. Set the pot over medium-high heat and bring to a boil. Once boiling, immediately reduce the heat to medium-low so that the mixture is at a low boil.

Preheat the oven to 375°F.

Cook the pasta, stirring occasionally, until it has absorbed most of the liquid, about 10 minutes.

Turn off the heat and remove the lid from the pot. Add the cream cheese to the noodles and stir.

Add the remaining milk, heavy cream, mustard powder, salt, and pepper to the pot. Stir to combine.

Add 2/3 of the cheddar cheese to the pot. Stir until the cheese is melted into the sauce.

Pour the mixture into the prepared baking dish, then sprinkle remaining cheese in an even layer on top.

Bake the mac and cheese on middle rack of oven until bubbling at edges and the top is lightly browned, 22-25 minutes.

Check to see that dish is done. Remove from oven or add time as needed.

Allow macaroni and cheese to rest for 15-20 minutes before serving.