Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente, about 8–10 minutes. Reserve ½ cup of pasta water, then drain the pasta and set aside.

In a large skillet, heat the olive oil or butter over medium heat. Add the sliced mushrooms and sauté for about 6–7 minutes until golden brown and tender.

Stir in the minced garlic, salt, and black pepper. Cook for 1–2 minutes until the garlic is fragrant. Add the fresh spinach and toss until wilted, about 2–3 minutes.

Pour in the heavy cream and add the grated Parmesan cheese. Stir gently to combine until the cheese melts and the sauce thickens, simmering on low heat for 2–3 minutes.

Add the cooked pasta into the skillet with the sauce. Toss to coat the pasta thoroughly, adding reserved pasta water as needed to reach desired consistency.

Sprinkle extra grated Parmesan on top before serving warm.