1. Bring a large pot of salted water to a boil, add the elbow macaroni, and cook until just al dente, 1–2 minutes less than the package directions; drain and set aside.

2. In a large saucepan or Dutch oven, melt the butter over medium heat, sprinkle in the flour, and whisk constantly for 1–2 minutes until smooth and lightly fragrant but not browned.

3. Slowly whisk in the milk and heavy cream until smooth, then stir in the Dijon mustard, garlic powder, onion powder, smoked paprika, salt, and pepper; continue cooking, whisking often, until the sauce gently bubbles and thickens enough to coat the back of a spoon.

4. Reduce the heat to low and add the shredded cheddar and Gruyère in small handfuls, whisking after each addition until completely melted and the sauce is velvety; stir in 1/4 cup of the grated Parmesan.

5. Add the drained macaroni to the cheese sauce and gently stir until every piece of pasta is well coated; taste and adjust seasoning if needed.

6. Transfer the macaroni and cheese to a greased 9×13-inch baking dish and smooth the top into an even layer.

7. In a small bowl, combine the panko breadcrumbs, melted butter, and remaining 1/4 cup Parmesan until the crumbs are evenly moistened, then sprinkle the mixture evenly over the pasta.

8. Bake at 375°F (190°C) for 20–25 minutes, or until the edges are bubbling and the top is deeply golden and crisp.

9. Let the mac and cheese rest for 5–10 minutes before serving, then garnish with chopped fresh parsley if desired and serve warm.