1 pound cooked pasta (penne, macaroni, or similar)
6 Tbsp butter, divided
1/4 c flour
2 1/2 c milk
1 tsp freshly grated nutmeg
4 oz Gruyere, shredded
4 oz white Cheddar, shredded
4 oz Brie, diced (rind removed)
1 1/2 c fresh breadcrumbs
2 tsp Sriracha (optional)
2 Tbsp freshly shredded Parmesan
salt & pepper
Preheat oven to 350.
Melt 4 Tbsp butter in a saucepot over medium heat. When the butter starts to bubble slightly, add the flour and cook for a minute or two. Add a little salt and some pepper (go easy on the salt because the cheese is salty). Add the milk and stir immediately to blend everything without lumps. Raise the heat a little bit, and cook, stirring constantly, until the bechamel sauce thickens enough to coat the back of the spoon. Add the nutmeg. Take the sauce off the heat and add 3/4 of the Gruyere, Cheddar and Brie cheeses. Stir until cheeses are melted and completely incorporated. Add the cheese sauce to the pasta and pour into a large casserole dish. If you want, at this point you can drizzle some Sriracha on the mac 'n' cheese. It adds a tiny bit of kick and brightens up the dish. Top with the rest of the Gruyere, Cheddar and Brie.
In a saucepan, melt the remaining 2 Tbsp butter and add the breadcrumbs. Cook, stirring gently, for a couple of minutes, until the crumbs are pretty evenly coated with melted butter. Spread the breadcrumbs evenly on the casserole and sprinkle with the shredded Parmesan. Bake for 30 minutes, until the casserole is bubbly and the topping is golden brown.