Cook the pasta according to package instructions in a large pot of salted boiling water until al dente. Drain and set aside, reserving ½ cup of pasta water.

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

Add the minced garlic and sliced mushrooms to the skillet. Cook for an additional 5-7 minutes until the mushrooms are browned and tender.

Stir in the fresh spinach and cook until wilted, about 2-3 minutes.

Lower the heat and pour in the heavy cream, stirring to combine. Add the grated Parmesan cheese, salt, pepper, and Italian seasoning. Mix until the cheese has melted and the sauce is creamy.

Add the cooked pasta to the skillet, tossing to coat the pasta in the sauce. If the sauce is too thick, add a little reserved pasta water until the desired consistency is reached.

Serve immediately, garnished with fresh parsley.