Add flour, paprika, salt, and pepper to melted butter, whisking until a paste is formed.
Add milk to the paste, whisking as you pour the milk. Whisk until the paste and milk are combined.
Heat milk mixture until it starts to thicken and bubble on the edges, stirring frequently.
When the milk mixture starts to thicken, add the cubed Velveeta, about a quarter of the cheese at a time. Stir frequently, and let the cheese melt before adding more.
Once all the cheese is melted, pour over the cooked pasta. Stir well to combine.
In a microwave-safe bowl, melt 3 Tablespoons butter. Add Panko bread crumbs, and mix with a fork to combine.
Sprinkle Panko crumbs on top of macaroni and cheese.
Bake, uncovered, at 350 degrees for 15-20 minutes, until hot and bubbly.
If desired, turn on broiler for 2-4 minutes until top is brown and crunchy.