Penne al Forno
1 ounce unsalted butter (2 tablespoons)
2 tablespoons flour
2 cups milk
1 cup creme fraiche (available at well-stocked grocery stores and cheese shops)
freshly grated nutmeg to taste (optional)
fine sea salt and freshly ground white pepper to taste
2 ounces Parmigiano Reggiano, finely grated (about 1/2 cup)
2 ounces Swiss or French Gruyere, finely grated (about 1/2 cup)
1 tablespoon Dijon mustard
8 ounces penne, cooked al dente
2 tablespoons unsalted butter
1 medium onion, finely chopped
2 ounces Panko bread crumbs, about 1 cup (available at well-stocked grocery stores and Asian markets)
Melt 2 tablespoons butter in a heavy saucepan. Stir in the flour and cook over low heat for 3 minutes or until the raw flour smell is gone and it begins to smell slightly nutty. Add the milk, whisking constantly, and continue whisking until the sauce comes to a boil. (Now is a good time to start your pasta). Reduce the heat and simmer for 10 minutes, or until slightly thickened, stirring occasionally. It should be able to coat the back of a wooden spoon well- pull your finger through the back of the spoon and the line should stay clear and not run back to the center or drip. When the sauce is of desired consistency (there should be about 1 1/2 cups of sauce), add the nutmeg to taste.
Whisk in the creme fraiche and keep warm on the burner at low heat. Add the grated cheeses and mustard and stir until the cheese melts and the sauce is smooth. Season to taste with salt and pepper. Set aside.
Drain your pasta, transfer to a large baking dish and toss with 1 tablespoon butter. Heat the remaining butter in a skillet and saute the onion until slightly softened, about 2 minutes. Mix the onion, pepper, and cheese sauce with the penne. Sprinkle with bread crumbs and bake in a preheated 425 oven for 15 minutes or until the bread crumbs are lightly toasted. Let stand 10 minutes before serving.