Bring a large pot of salted water to a boil. Add the pasta and cook until al-dente, about 9-10 minutes. Drain, reserving about a cup of the water.
While the pasta cooks, in a large sauté pan over medium heat, add the oil. Add the sausage and sauté until brown, about 3 minutes. Add the onion and garlic and sauté until translucent, about 5 minutes. Add the wine and bring to a simmer. Cook until the liquid has reduced by half, about 8 minutes. Add the tarragon, cream and mustard and continue to simmer until the sauce is slightly thickened, about 5 minutes. Season to taste with salt, pepper and nutmeg.
Toss the pasta in the sauce and divide between 4 warmed plates or pasta bowls. Top with grated cheese.
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