How to Make It
Bring a large pot of salted water to a boil. Cook penne according to package directions.
Meanwhile, heat butter and oil in a skillet over medium-high heat. Cook onions for 10-15 minutes, stirring often. Once they’ve become caramelized, add the mushrooms and cook another 4-5 minutes. Season with salt and pepper to taste. Remove from the pan, and set aside.
In the same pan, add the chicken thighs. (If needed, add another drizzle of oil.) Cook for 7-10 minutes, or until golden brown on both sides and cooked through. Remove from pan and set aside.
Return onion and mushroom mixture to the skillet. Add heavy cream, and stir well, scraping all the bits from the bottom the pan. Simmer on medium-low for 2-3 minutes, or until cream has reduced slightly. Taste for seasoning, and adjust as needed. Slice the chicken into large pieces.
Add the cooked, drained pasta to the sauce, along with the sliced chicken and parsley. Toss well, and serve with freshly grated Parmesan cheese.