Bring a large pot of salted water to a boil and cook the penne pasta according to package instructions until al dente; drain and set aside.

While the pasta cooks, clean and slice the mushrooms, mince the garlic, and finely chop the onion.

Cut the chicken breasts into bite-sized pieces and season them with salt and pepper.

Heat olive oil in a large skillet over medium-high heat and add the seasoned chicken pieces; cook until browned and cooked through, about 6-8 minutes. Remove chicken from the skillet and set aside.

In the same skillet, add the chopped onion and sauté for 2-3 minutes until translucent, then add the garlic and mushrooms and cook until the mushrooms are tender and golden, about 5 minutes.

Pour in the chicken broth and heavy cream, stirring to combine, then add the dried thyme and bring the sauce to a gentle simmer.

Return the cooked chicken to the skillet, add the drained pasta, and stir in the grated Parmesan cheese until the sauce thickens and coats the pasta evenly.

Adjust seasoning with salt and pepper as needed, then sprinkle chopped fresh parsley on top before serving.