Preheat and prep: Heat your oven to 375°F (190°C). Grease a 9x13-inch baking dish or similar casserole.

Cook the pasta: Boil in well-salted water until 1 to 2 minutes shy of al dente. Drain and set aside. Toss with a teaspoon of olive oil to prevent sticking.

Warm the dairy: In a small pot, gently warm the milk and cream. Warm dairy blends more smoothly into the roux.

Make the roux: In a large pot over medium heat, melt 4 tablespoons butter. Add flour and whisk for 1 to 2 minutes until it smells toasty but not browned.

Build the sauce: Slowly whisk in the warm milk and cream. Keep whisking until smooth. Simmer 3 to 5 minutes, stirring often, until slightly thick and glossy.

Season smartly: Stir in garlic, Dijon, smoked paprika, nutmeg, 1 teaspoon salt, and a few grinds of pepper. Taste and adjust. You want it a touch saltier than you think—pasta will mute it.

Add the cheeses: Reduce heat to low. Add cheddar and Gruyère by handfuls, whisking until melted before adding more. Stir in Parmesan last. Do not boil.

Combine with pasta: Fold the pasta into the sauce. If using extras like bacon or mushrooms, fold them in now. The mixture should be creamy and just loose enough to flow into the dish.

Make the topping: In a bowl, mix panko with 2 tablespoons melted butter, 1 tablespoon olive oil, a pinch of salt, and extra Parmesan if you like. It should feel slightly damp and clumpy.

Assemble and bake: Transfer mac and cheese to the baking dish. Sprinkle the panko topping evenly. Bake 18 to 22 minutes, until bubbling at the edges and golden on top.

Rest and serve: Let it sit 5 to 10 minutes so the sauce sets slightly. Garnish with chopped herbs and a pinch of red pepper flakes if you want a little kick.