Cook the pasta according to the package directions, omitting salt and fat; drain.
Heat a Dutch oven over medium-high heat;coat with cooking spray. Sprinkle chicken with 1/4 teaspoon salt and 1/4 teaspoon black pepper. Add the chicken to the pan; saute 4 minutes, turning to brown on all sides. Add the stock and bring to a boil. Cook for 2 minutes. Remove from the heat; stir in 1/4 teaspoon salt, 1/4 teaspoon black pepper, mascarpone, and 2 tablespoons parsley.
While the pasta is cooking begin preheating the oven to 450 degrees. While preheating, combine the butternut squash, shallots, garlic, and shiitake mushrooms. Drizzle the mixture with 1 tablespoon olive oil; toss.
Transfer the squash mixture to a small roasting pan; sprinkle with 1/4 teaspoon kosher salt and 1/4 teaspoons black pepper. Bake at 450 degrees for 20 minutes or until the vegetables are just tender.
Add the vegetable mixture to the pasta mixture. Cook 1 minute or until thoroughly heated. Sprinkle with chives and the remaining 1/4 teaspoon of salt and pepper.