Cook the 12 oz elbow macaroni in well-salted boiling water for 2 minutes less than the package directs. Drain and set aside.

Melt the 4 tbsp unsalted butter in a large saucepan over medium heat. Add the 3 tbsp flour and whisk for 90 seconds until pale golden.

Slowly whisk in the 2 cups whole milk and 1 cup heavy cream. Cook over medium heat for 4 to 5 minutes, whisking, until thickened. Reduce to low and stir in the 1 tsp Dijon mustard, 1/2 tsp garlic powder, 1/2 tsp onion powder, 1/4 tsp cayenne, 1 tsp salt, and 1/2 tsp black pepper. Add the 2 cups cheddar and 1 cup Gruyère in small handfuls, stirring until smooth between each addition.

Remove from heat. Fold in the drained pasta and pour into a greased 9x13-inch baking dish. Preheat oven to 375°F (190°C).

Toss the 1/2 cup panko with the 2 tbsp melted butter and scatter over the top. Bake uncovered for 22 to 25 minutes until the topping is golden and the sauce bubbles at the edges.

Let rest for 5 minutes, then scoop onto plates and finish with a pinch of smoked paprika and cracked black pepper.