1) Prep and heat
Heat oven to 375°F if you plan to bake. Bring a large pot of water to a boil.
2) Cook the pasta (keep it bouncy)
Salt the boiling water generously (about 1 to 2 tbsp kosher salt for a large pot with 4 to 6 quarts water), then cook macaroni 1 to 2 minutes shy of the box directions. Before draining, scoop out 1/2 cup pasta water. Drain pasta and return it to the large pot (off heat).
3) Make the roux
In a large saucepan or Dutch oven (4 to 6 quarts) over medium heat, melt butter. Whisk in flour and cook for 1 minute, whisking constantly, until it smells lightly toasty and looks like wet sand.
4) Build the sauce
Slowly whisk in whole milk, then evaporated milk. Bring to a gentle simmer, whisking often, and cook 3 to 5 minutes until it thickens to coat the back of a spoon. It should look a little looser than your final goal because it will tighten slightly once the cheese goes in.
Whisk in Dijon, smoked paprika, garlic powder, cayenne (if using), salt, and black pepper.
5) Add cheese the right way
Turn heat to low. Keep the sauce below a simmer. Add cheddar and Monterey Jack in 3 to 4 handfuls, stirring until melted before adding more. Stir in Parmesan. If using hot sauce, add it now.
If the sauce feels too thick, stir in reserved pasta water a little at a time until it is glossy and pours slowly.
6) Combine (no spills)
Pour the cheese sauce over the cooked pasta in the large pot and fold until every noodle is coated. Taste and adjust salt, pepper, paprika, mustard, or hot sauce.
7) Choose your finish
Stovetop creamy: Let it sit 2 minutes, then serve immediately.
Baked crispy edges: Pour into a greased 9x13-inch baking dish.
8) (Optional) Add the topping
Mix panko with melted butter, Parmesan, and a pinch of paprika. Sprinkle evenly over the mac.
9) Bake fast, do not dry it out
Bake now (hot casserole): Bake uncovered for 12 to 15 minutes, just until bubbling around the edges and the center looks hot and glossy. If you like numbers, you are aiming for an internal temp around 165°F.
Bake from cold (make-ahead): Take the dish out of the fridge while the oven heats. Stir 2 to 4 tbsp milk into the mac if it looks tight. Cover with foil and bake 20 minutes, then uncover and bake 10 to 15 minutes more until bubbling and hot in the center. Broil 1 to 2 minutes at the end for extra color, watching closely.
Rest 5 minutes before serving so the sauce settles into that fluffy, moist sweet spot.
