01 -
Preheat oven to 175°C. Grease a 23 x 33 centimeter baking dish with cooking spray or melted butter and set aside.
02 -
In a small bowl, mix together panko breadcrumbs, melted butter, and seasoned salt. Set mixture aside.
03 -
Bring a large pot of generously salted water to a boil. Cook macaroni until just shy of al dente, about 2 minutes less than package instructions. Drain and transfer to a large bowl. Toss pasta with a drizzle of olive oil or butter to prevent sticking.
04 -
Melt butter in a large saucepan over medium-high heat. Add flour and whisk continuously for 1 minute. Gradually pour in whole milk in a steady stream, whisking constantly, then add half and half. Continue whisking until mixture is smooth.
05 -
Add black pepper, nutmeg, garlic powder, and dried mustard to the sauce. Continue whisking and bring the mixture to a simmer, stirring until thickened and it coats the back of a spoon, about 6–8 minutes.
06 -
Reduce heat to low. Add sharp cheddar cheese in small amounts, stirring until melted before adding more. Repeat process with white cheddar and Gruyère cheese until sauce is smooth and creamy. Remove saucepan from heat.
07 -
Pour the cheese sauce over the cooked macaroni and mix thoroughly. Add remaining white cheddar cheese and continue mixing until evenly distributed. Adjust seasoning with salt and pepper as needed.
08 -
Transfer coated macaroni to the prepared baking dish and spread evenly. Sprinkle panko topping over the surface. Bake for 20 minutes until the top is golden brown. For a deeper golden finish, broil for 2–3 minutes under supervision.
09 -
Remove the dish from the oven and allow it to rest for 10 minutes before serving to ensure proper setting.