01 - Preheat the oven to 350°F if baking with a topping.
02 - Boil elbow macaroni in salted water until al dente. Drain and set aside.
03 - Melt butter in a saucepan over medium heat. Whisk in flour and cook 1–2 minutes until lightly golden, stirring constantly.
04 - Gradually whisk in milk and heavy cream, avoiding lumps. Simmer gently until sauce thickens, about 3–5 minutes.
05 - Reduce heat to low, stir in sharp cheddar and Gruyère until melted and smooth. Season with salt, pepper, mustard powder, and paprika as desired.
06 - Add cooked macaroni to cheese sauce, stirring to coat evenly.
07 - Transfer mixture to a greased baking dish. Mix panko, Parmesan, and melted butter; sprinkle over pasta. Bake uncovered for 15–20 minutes until golden and bubbly.
08 - Serve hot, garnished with fresh herbs if desired.