Cook the rigatoni pasta according to package instructions until al dente. Drain and set aside.

In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for about 3-4 minutes until translucent.

Add the minced garlic and sliced mushrooms to the skillet. Cook for 5-7 minutes until the mushrooms have released their moisture and are golden brown.

Stir in the heavy cream, thyme, salt, and black pepper. Bring to a simmer and cook for an additional 5 minutes, allowing the sauce to thicken.

Add the cooked rigatoni to the skillet and toss to coat the pasta in the mushroom sauce.

Remove from heat and stir in the grated parmesan cheese until melted and well combined.

Serve hot, garnished with chopped fresh parsley.