Bring a large pot of salted water to a vigorous boil (about 1 tbsp salt per 4–6 quarts water). Add 12 oz elbow macaroni and cook until just al dente according to package directions (usually 1–2 minutes less than full time). Reserve 1 cup of the pasta cooking water, then drain the pasta and set aside.

Make a roux

In a medium heavy-bottomed saucepan over medium heat, melt 4 tbsp butter. Add 3 tbsp all-purpose flour and whisk continuously for 1 to 1½ minutes until the mixture bubbles and is lightly golden (this cooks the raw flour taste).

Add dairy

Slowly whisk in 2 cups whole milk and 1 cup half-and-half, a little at a time, until smooth. Continue to cook over medium heat, stirring frequently, until the sauce begins to thicken and coats the back of a spoon, about 6–8 minutes.

Season the sauce

Whisk in 1 tsp mustard powder, 1 tsp garlic powder, 1.5 tsp salt, 0.5 tsp black pepper, and 1/8 tsp nutmeg. Taste and adjust seasoning—remember cheeses will add salt.

Finish the cheese sauce

Reduce heat to low. Add 3 cups sharp cheddar, 1 cup medium cheddar, and 2 oz softened cream cheese in handfuls, stirring after each addition until fully melted and smooth. Stir in 1 tsp Worcestershire sauce. If sauce is too thick, whisk in up to 1/2 cup reserved pasta cooking water, 1 tbsp at a time, until desired consistency is reached.

Combine pasta and sauce

Add drained pasta to the cheese sauce and gently stir to coat evenly. Cook together on low for 1–2 minutes to let flavors marry. If serving immediately and sauce tightens, stir in a splash of reserved pasta water or milk to loosen.

Topping & bake (optional)

Preheat oven

Preheat the oven to 375°F (190°C) if you want a baked topping. Grease a 9x9-inch (or similar) baking dish lightly with butter.

Prepare topping

In a small bowl combine 3 tbsp panko breadcrumbs, 2 tbsp grated Parmesan, 1 tbsp melted butter, and 1 tbsp chopped parsley. Toss until breadcrumbs are evenly coated.

Assemble and bake

Transfer the mac & cheese into the prepared baking dish, smooth the top, and evenly sprinkle the breadcrumb mixture. Bake in the preheated oven until the topping is golden and the casserole is bubbling at the edges, about 15–20 minutes. For extra brownness, broil 1–2 minutes—watch closely to avoid burning.

Alternative stovetop finish

If you prefer not to bake, simply sprinkle the breadcrumb mixture over portions and broil in a preheated broiler for 1–2 minutes or skip the topping entirely. Serve hot.

Serve

Let the baked mac & cheese rest 5 minutes before serving to set slightly. Garnish with additional chopped parsley if desired.