Bring a large pot of cold water to a boil and salt it generously. Add the noodles, and cook, stirring occasionally, until al dente, about 8 to 10 minutes.
Mix about 1 tablespoon of skim milk with the cornstarch and set aside. Heat the remaining skim milk in a saucepan over medium heat with the parsley, thyme, and bay leaf. When fragrant, whisk in the cornstarch mixture and bring to a boil over high heat, and simmer until the milk thickens. Remove the herbs and stir in the cheese, until melted. Whisk the butter, mustard, salt, nutmeg, and cayenne into the sauce.
Drain the pasta and transfer to a large bowl. Toss with the cheese sauce and season with salt and black pepper. Serve.
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