01 -
Preheat oven to 180°C and lightly grease a 3-litre casserole dish.
02 -
Boil elbow macaroni in a large pot of salted water just until al dente according to package instructions. Drain thoroughly, then stir in unsalted butter to coat. Transfer macaroni to the prepared casserole dish and spread evenly. Allow to cool slightly.
03 -
While pasta cooks, freshly shred the cheddar, Gruyère, and mozzarella cheeses. Set aside 1 cup (about 115 g) of shredded cheddar for the topping. Combine the remaining cheddar, Gruyère, and mozzarella in a bowl.
04 -
Melt unsalted butter in a wide, deep skillet over medium heat. Whisk in the flour and cook, whisking constantly, until the mixture loses its raw flour aroma and begins to foam without browning, about 1 to 2 minutes.
05 -
Gradually whisk in the warmed milk, maintaining medium heat to avoid lumps or splatter. Stir continuously until the mixture is smooth and slightly thickened, about 5 minutes. Add half-and-half (or cream) and cook for an additional 1 to 2 minutes. Remove from heat. Stir in Dijon mustard, salt, onion powder, garlic powder, paprika, nutmeg, and black pepper. Add the mixed cheeses (excluding reserved cheddar) and stir until melted and sauce becomes velvety smooth.
06 -
Pour the cheese sauce over the macaroni and stir gently to coat all pasta. Smooth the top in the casserole dish.
07 -
Evenly sprinkle reserved shredded cheddar over the assembled macaroni. In a separate bowl, thoroughly mix panko breadcrumbs with melted unsalted butter and salt. Scatter breadcrumb mixture evenly over the top.
08 -
Bake in the preheated oven for 20 to 25 minutes, until the edges are bubbling and the topping is lightly golden. Avoid overbaking to preserve a creamy interior. Rest for 5 to 10 minutes after baking before serving warm.