Fill a large pot with water, add a generous pinch of salt, and bring to a rolling boil. Add the elbow macaroni and cook al dente, about 1 minute less than package directions suggest. Reserve ½ cup of starchy pasta water before draining. Do not rinse the pasta.
While the pasta cooks, cut the Velveeta block into 1-inch uniform cubes. Set them aside in a bowl ready for melting.
In a medium saucepan or deep skillet, combine the whole milk and heavy cream. Warm over medium-low heat until hot but not boiling, with small wisps of steam rising from the surface.
Add the butter to the warm dairy and stir until melted. Add the cubed Velveeta a few pieces at a time, stirring constantly with a wooden spoon or silicone spatula. Keep the heat on medium-low and continue stirring until every cube has melted and the sauce is smooth, about 5-7 minutes.
Stir in the garlic powder, onion powder, and smoked paprika (if using) until evenly distributed. Taste the sauce and adjust with salt and black pepper as needed, remembering that Velveeta already contains sodium.
Add the drained elbow macaroni directly into the pan with the cheese sauce. Stir well until every piece of pasta is thoroughly coated. If the sauce is too thick, add the reserved pasta water a tablespoon at a time until you reach the desired consistency. If it's too thin, let it sit over low heat for 1-2 minutes, stirring occasionally, to thicken.
Do a final taste test and adjust seasonings as needed. Garnish with fresh chopped parsley and an extra sprinkle of smoked paprika, if desired. Serve immediately while the sauce is at its creamiest.