Preheat the oven to 350°F (175°C).
Place the Velveeta in the center of a cast iron skillet or baking dish.
Add the dry elbow macaroni, evenly distributing it around the Velveeta.
Pour in the milk, making sure all the pasta is covered.
Sprinkle the shredded cheese over the top.
Distribute the butter pieces evenly across the dish.
Season with salt, pepper, ground mustard, and garlic powder—but do not stir.
Bake for 25 minutes, then carefully remove from the oven and stir everything together.
Return to the oven and bake for an additional 10 minutes, until the cheese is fully melted and the dish is bubbly.