1) Cook the pasta according to the package directions. Reserve 1/2 cup of the pasta water, set it aside. Drain your pasta and return it to the pot.
2) Meanwhile, heat the olive oil in a large skillet over medium-high heat. Add the mushrooms and onion, cook, tossing occassionally, until the mushrooms begin to release their juices, 2-3 minutes. Add, the wine, 1/2 teaspoon salt, some pepper to your liking. Cook until the mushrooms begin to brown, 5-6 minutes.
3) Toss the pasta with the Brie and a little of the reserved pasta water (1-2 tablespoons at a time, just to add some cozy saucey-ness) until the pasta is totally coated and cheese is pretty melted. Stir in the mushroom mixture and arugula. DONE! If you have some, sprinkle some Parmesan on top. And some fresh cracked pepper.