Boil elbow macaroni in well-salted water until just under al dente. Drain and set aside.
Melt 4 tbsp butter in a large saucepan over medium heat.
Whisk in 4 tbsp flour and cook 1–2 minutes until light golden.
Slowly whisk in 3 cups warm milk and 1 cup heavy cream.
Simmer until thick, about 5 minutes.
Stir in 4 oz cream cheese until smooth.
Remove from heat and add 2½ cups sharp cheddar, 1 cup Gruyère, ½ cup mozzarella, 1 tsp Dijon mustard, ½ tsp garlic powder, and ½ tsp smoked paprika. Stir until silky.
Mix cooked pasta into cheese sauce. Taste and adjust salt and pepper.
Pour mixture into a buttered baking dish.
Mix 1 cup panko breadcrumbs with 2 tbsp melted butter and ½ cup shredded cheddar. Sprinkle on top.
Bake at 375°F (190°C) for 20–25 minutes until bubbly and golden.
Broil for 1–2 minutes for extra crunch, watching closely.
Let sit 5–10 minutes before serving.
