Cook the Macaroni:
Bring a large pot of salted water to a boil.
Add 1 lb of elbow macaroni (or your choice of pasta) and cook according to the package instructions until al dente.
Drain the pasta and set aside.
Prepare the Cheese Sauce:
In a saucepan, melt 4 tbsp of butter over medium heat.
Add 4 tbsp of flour to the melted butter, stirring to form a roux. Cook for 2 minutes to eliminate the raw flour taste.
Gradually add 2 cups of milk, whisking constantly to prevent lumps.
Continue whisking until the sauce thickens and begins to bubble.
Stir in 1 ½ cups of shredded Gruyère cheese and 1 cup of grated Parmesan cheese. Stir until smooth and the cheese is fully melted.
Season the sauce with salt, pepper, and a pinch of nutmeg if desired.
Combine Pasta and Sauce:
Add the cooked pasta to the saucepan with the cheese sauce and stir to coat the pasta evenly.
Pour the pasta and sauce into a greased baking dish.
Create the Topping:
In a small bowl, mix 1 cup of breadcrumbs (preferably panko) with 2 tbsp of melted butter.
Add extra grated cheese if desired and stir until the breadcrumbs are well coated.
Sprinkle the breadcrumb mixture evenly over the top of the macaroni and cheese.
Bake:
Preheat your oven to 350°F (175°C).
Bake for 25-30 minutes, or until the top is golden and crispy, and the cheese is bubbling.
Remove from the oven and let rest for a few minutes before serving.
Serve:
Scoop portions onto plates and garnish with fresh parsley if desired.
Serve hot and enjoy your delicious Gratin de Macaroni!