Pasta with Brie, Mushrooms and Arugula

Ingredients
12 ounces penne (3/4 box)
1 tablespoon olive oil
1 pound button mushrooms, quartered
1 small red onion, sliced
1/2 cup dry white wine
kosher salt and black pepper
8 ounces Brie, cut into 1-inch pieces
4 cups baby arugula

Directions
Cook the pasta according to the package directions. Reserve ½ cup of the pasta water, drain the pasta, and return it to the pot.
Meanwhile, heat the oil in a large skillet over medium-high heat. Add the mushrooms and onion and cook, tossing occasionally, until the mushrooms begin to release their juices, 2 to 3 minutes. Add the wine, ½ teaspoon salt, and ¼ teaspoon pepper and cook until the mushrooms begin to brown, 5 to 6 minutes.
Toss the pasta with the Brie and reserved pasta water until the pasta is coated. Stir in the mushroom mixture and arugula.